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Monday, October 9, 2023

Christian mission

From Wikipedia, the free encyclopedia

A Christian mission is an organized effort for the propagation of the Christian faith. Missions involve sending individuals and groups across boundaries, most commonly geographical boundaries, to carry on evangelism or other activities, such as educational or hospital work. Sometimes individuals are sent and are called missionaries, and historically may have been based in mission stations. When groups are sent, they are often called mission teams and they do mission trips. There are a few different kinds of mission trips: short-term, long-term, relational and those that simply help people in need. Some people choose to dedicate their whole lives to mission. Missionaries preach the Christian faith (and sometimes to administer sacraments), and provide humanitarian aid. Christian doctrines (such as the "Doctrine of Love" professed by many missions) permit the provision of aid without requiring religious conversion. However, Christian missionaries are implicated in the genocide of indigenous peoples. Around 100,000 native people in California, U.S., or 1/3 of the native population, are said to have died due to missions.

History of Christian missions

The earliest Christian mission, the Great Commission and Dispersion of the Apostles, was active within Second Temple Judaism. Whether a Jewish proselytism existed or not that would have served as a model for the early Christians is unclear; see Circumcision controversy in early Christianity#Background for details. Soon, the expansion of the Christian mission beyond Judaism to those who were not Jewish became a contested issue, notably at the Council of Jerusalem. The Apostle Paul was an early proponent of this expansion, and contextualized the Christian message for the Greek and Roman cultures, allowing it to reach beyond its Hebrew and Jewish roots.

From Late Antiquity onward, much missionary activity was carried out by members of religious orders. Monasteries followed disciplines and supported missions, libraries, and practical research, all of which were perceived as works to reduce human misery and suffering and glorify the Christian God. For example, Nestorian communities evangelized parts of Central Asia, as well as Tibet, China, and India. Cistercians evangelized much of Northern Europe, as well as developing most of European agriculture's classic techniques. St Patrick evangelized many in Ireland. St David was active in Wales.

During the Middle Ages, Ramon Llull advanced the concept of preaching to Muslims and converting them to Christianity by means of non-violent argument. A vision for large-scale mission to Muslims would die with him, not to be revived until the 19th century.

Additional events can be found at the timeline of Christian missions.

Medieval

During the Middle Ages, Christian monasteries and missionaries such as Saint Patrick, and Adalbert of Prague propagated learning and religion beyond the boundaries of the old Roman Empire. In the seventh century Gregory the Great sent missionaries, including Augustine of Canterbury, into England, and in the eight century English Christians, notably Saint Boniface, spread Christianity into Germany. The Hiberno-Scottish mission began in 563.

In the late thirteenth and early fourteenth centuries, Franciscans such as William of Rubruck, John of Montecorvino, and Giovanni ed' Magnolia were sent as missionaries to the Near and Far East. Their travels took them as far as China in an attempt to convert the advancing Mongols, especially the Great Khans of the Mongol Empire. (Also see Medieval Roman Catholic Missions in China). In the later part of the fifteenth century, Portuguese missionaries had some success in spreading Christianity to the Kingdom of Kongo in West Africa

Catholic missions after 1492

The Mission San Gabriel Arcángel in San Gabriel, California

One of the main goals of the Christopher Columbus expedition financed by Queen Isabella of Spain was to spread Christianity. During the Age of Discovery, Spain and Portugal established many missions in their American and Asian colonies. The most active orders were the Jesuits, Augustinians, Franciscans and Dominicans. The Portuguese sent missions into Africa. These are some of the most well-known missions in history. While some of these missions were associated with imperialism and oppression, others (notably Matteo Ricci's Jesuit mission to China) were relatively peaceful and focused on inculturation rather than cultural imperialism.

In both Portugal and Spain, religion was an integral part of the state and evangelization was seen as having both secular and spiritual benefits. Wherever these powers attempted to expand their territories or influence, missionaries would soon follow. By the Treaty of Tordesillas, the two powers divided the world between them into exclusive spheres of influence, trade and colonization. The proselytization of Asia became linked to Portuguese colonial policy.

From 1499 onward, Portuguese trade with Asia rapidly proved profitable. As Jesuits arrived in India around 1540 the colonial government in Goa supported the mission with incentives for baptized Christians. Beginning in 1552, the Church sent Jesuits to China and to other countries in Asia.

During the time of the Holland (Batavia) Mission (1592–1853), when the Roman Catholic church in the country was suppressed, there were neither parishes nor dioceses, and the country effectively became a mission area in which congregations were called "stations" (staties). Statie, usually called a clandestine church in English, refers to both the congregation's church and its seat or location.

Protestant missions

Lähetystalo, the office and church building of the Finnish Evangelical Lutheran Mission in Ullanlinna, Helsinki, Finland in 1903

The Reformation unfolded in Europe in the early 16th century. For over a hundred years, occupied by their struggle with the Catholic Church, the early Protestant churches as a body were not strongly focused on missions to "heathen" lands. Instead, the focus was initially more on Christian lands in the hope to spread the Protestant faith, identifying the papacy with the Antichrist.

In the centuries that followed, Protestant churches began sending out missionaries in increasing numbers, spreading the proclamation of the Christian message to previously unreached people. In North America, missionaries to the Native Americans included Jonathan Edwards (1703–1758), the well-known preacher of the Great Awakening (c. 1731–1755), who in his later years retired from the very public life of his early career. He became a missionary to the Housatonic Native Americans (1751) and a staunch advocate for them against cultural imperialism.

As European culture has been established in the midst of indigenous peoples, the cultural distance between Christians of differing cultures has been difficult to overcome. One early solution was the creation of segregated "praying towns" of Christian natives. This pattern of grudging acceptance of converts played out again later in Hawaii when Congregational missionaries from New England went there and converted the native population, including the royalty. In the course of the Spanish colonization of the Americas, the Catholic missionaries learned the languages of the Amerindians and devised writing systems for them. Then they preached to indigenous people in those languages (Quechua, Guarani, Nahuatl) instead of Spanish, to keep Indians away from "sinful" whites. An extreme case of segregation occurred in the Guarani Reductions, a theocratic semi-independent region established by the Jesuits in the region of the future Paraguay between the early 17th century and 1767.

From 1732 onwards the Moravian Church began sending out missionaries.

Around 1780, an indigent Baptist cobbler named William Carey began reading about James Cook's travels voyages in Polynesia. His interest grew to a furious sort of "backwards homesickness", inspiring him to obtain Baptist orders, and eventually to write his famous 1792 pamphlet, "An Enquiry into the Obligation of Christians to use Means for the Conversion of Heathen". Far from a dry book of theology, Carey's work used the best available geographic and ethnographic data to map and count the number of people who had never heard the Gospel. It inspired a movement that has grown with increasing speed from his day to the present.

In the United States, the American Board of Commissioners for Foreign Missions (ABCFM) was chartered in 1812.

Protestant missionaries from the Anglican, Lutheran and Presbyterian traditions starting arriving in what was then the Ottoman Empire in the first half of the 19th Century. This eventually let to the creation of what are today the Evangelical Lutheran Church in Jordan and the Holy Land and the see of the Anglican Bishop in Jerusalem. Furthermore, it was during this time that the Christian and Missionary Alliance started their missionary activity in Jerusalem.

American "Hard Shell Baptists", "Anti-Mission Baptists", or "Old School Baptists" adhering to strict Calvinism rejected all mission boards, Bible tract societies, and temperance societies as nonbiblical. This faction was strongest in the American South. The mainstream of the Baptist denomination, however, supported missionary work.

Thomas Coke, (1747–1814) the first bishop of the American Methodists, was "the Father of Methodist Missions". After spending time in the newly formed United States of America strengthening the infant Methodist Church alongside Episcopal colleague Francis Asbury, the British-born Coke left for mission work. During his time in America, Coke worked vigorously to increase Methodist support of Christian missions and of raising up mission workers. Coke died while on a mission trip to India, but his legacy among Methodists – his passion for missions – continues.

China

Missionary preaching in China using The Wordless Book

A wave of missions, starting in the early 1850s, targeted inland areas, led by a Briton Hudson Taylor (1832–1905) with his China Inland Mission (1865– ). Taylor was later supported by Henry Grattan Guinness (1835–1910) who founded (1883) Cliff College, which continues as of 2014 to train and equip for local and global mission.

The missions inspired by Taylor and Guinness have collectively been called "faith missions" and owe much to the ideas and example of Anthony Norris Groves (1795–1853). Taylor, a thorough-going nativist, offended the missionaries of his era by wearing Chinese clothing and speaking Chinese at home. His books, speaking, and examples led to the formation of numerous inland missions and of the Student Volunteer Movement (SVM, founded in 1886), which from 1850 to about 1950 sent nearly 10,000 missionaries to inland areas, often at great personal sacrifice. Many early SVM missionaries traveling to areas with endemic tropical diseases left with their belongings packed in a coffin, aware that 80% of them would die within two years.

British Empire

In the 18th century, and even more so in the 19th century, missionaries based in Britain saw the British Empire as a fertile field for proselytizing for Christianity. All the main denominations were involved, including the Church of England, Scottish Presbyterian, and Nonconformists. Much of the enthusiasm emerged from the Evangelical revival. Within the Church of England, the Church Mission Society (CMS) originated in 1799 and went on to undertake activity all around the world, including in what became known as "the Middle East".

Before the American Revolution, British Anglican and Methodist missionaries were active in the Thirteen Colonies. The Methodists, led by George Whitefield, were the most successful and after the Revolution an entirely distinct American Methodist denomination emerged that became the largest Protestant denomination in the United States. A major problem for British colonial officials was the demand of the Church of England to set up an American bishop; this was strongly opposed by most of the Americans colonists, as it had never happened before. Colonial officials increasingly took a neutral position on religious matters, even in those colonies such as Virginia where the Church of England was officially established, but in practice controlled by laymen in the local vestries. After the American War of Independence, colonial officials decided to enhance the power and wealth of the Church of England in all British colonies, including British North America.

Missionary societies funded their own operations that were not supervised or directed by the Colonial Office. Tensions emerged between the missionaries and the colonial officials. The latter feared that missionaries might stir up trouble or encourage the natives to challenge colonial authority. In general, colonial officials were much more comfortable with working with the established local leadership, including the native religions, rather than introducing the divisive force of Christianity. This proved especially troublesome in India, were very few local elites were attracted to Christianity. In Africa, especially, the missionaries made many converts. As of the 21st century there were more Anglicans in Nigeria than in England.

Christian missions in Australia played a part in both indoctrinating Aboriginal Australians into Christianity, and in controlling their movements and removing children from families, leading to the Stolen Generations. German missionaries ran Lutheran and other mission stations and schools, from the earliest days of colonisation of Australia. One of the largest organisations was the United Aborigines Mission, which ran dozens of missionaries and stations in Western Australia, New South Wales and South Australia in the 1900s.

Missionaries increasingly came to focus on education, medical help, and long-term modernization of the native personality to inculcate European middle-class values. They established schools and medical clinics. Christian missionaries played a public role, especially in promoting sanitation and public health. Many were trained as physicians, or took special courses in public health and tropical medicine at Livingstone College, London.

After 1870

By the 1870s, Protestant missions around the world generally acknowledged the long-term material goal was the formation of independent, self-governing, self-supporting, self-propagating churches. The rise of nationalism in the Third World provoked challenges from critics who complained that the missionaries were teaching Western ways, and ignoring the indigenous culture. The Boxer Rebellion in China in 1899–1901 involved bloody attacks on Christian missions and especially their converts. The First World War diverted resources, and pulled most Germans out of missionary work when that country lost its empire. The worldwide Great Depression of the 1930s was a major blow to funding mission activities.

In 1910, the Edinburgh Missionary Conference was presided over by active SVM and YMCA leader John R. Mott, an American Methodist layperson, the conference reviewed the state of evangelism, Bible translation, mobilization of church support, and the training of indigenous leadership. Looking to the future, conferees worked on strategies for worldwide evangelism and cooperation. The conference not only established greater ecumenical cooperation in missions, but also essentially launched the modern ecumenical movement.

The next wave of missions was started by two missionaries, Cameron Townsend and Donald McGavran, around 1935. These men realized that although earlier missionaries had reached geographic areas, there were numerous ethnographic groups that were isolated by language, or class from the groups that missionaries had reached. Cameron formed Wycliffe Bible Translators to translate the Bible into native languages. McGavran concentrated on finding bridges to cross the class and cultural barriers in places like India, which has upwards of 4,600 peoples, separated by a combination of language, culture, and caste. Despite democratic reforms, caste and class differences are still fundamental in many cultures.

An equally important dimension of missions strategy is the indigenous method of nationals reaching their own people. In Asia this wave of missions was pioneered by men like Dr G. D. James of Singapore, Rev Theodore Williams of India and Dr David Cho of Korea. The "two thirds missions movement" as it is referred to, is today a major force in missions.

Most modern missionaries and missionary societies have repudiated cultural imperialism, and elected to focus on spreading the gospel and translating the Bible. Sometimes, missionaries have been vital in preserving and documenting the culture of the peoples among whom they live.

Often, missionaries provide welfare and health services, as a good deed or to make friends with the locals. Thousands of schools, orphanages, and hospitals have been established by missions. One service provided by missionaries was the Each one, teach one literacy program begun by Dr. Frank Laubach in the Philippines in 1935. The program has since spread around the world and brought literacy to the least enabled members of many societies.

During this period missionaries, especially evangelical and Pentecostal missionaries, witnessed a substantial increase in the number of conversions of Muslims to Christianity. In an interview published in 2013 a leader of a key missionary agency focused on Muslims claimed that the world is living in a "day of salvation for Muslims everywhere."

The word "mission" was historically often applied to the building, the "mission station" in which the missionary lives or works. In some colonies, these mission stations became a focus of settlement of displaced or formerly nomadic people. Particularly in rural Australia, mission stations (known as missions) became home to many Indigenous Australians.

Additional events can be found at the Timeline of Christian missions.

Contemporary concepts of mission

Sending and receiving nations

Major nations not only send and fund missionaries abroad, but also receive them from other countries. In 2010, the United States sent out 127,000 missionaries, while 32,400 came to the United States. Brazil was second, sending out 34,000, and receiving 20,000. France sent out 21,000 and received 10,000. Britain sent out 15,000 and received 10,000. India sent out 10,000 and received 8000. Other major exporters included Spain at 21,000 sent out, Italy at 20,000, South Korea at 20,000, Germany at 14,000, and Canada at 8,500. Large recipient nations included Russia, receiving 20,000; Congo receiving 15,000; South Africa, 12,000; Argentina, 10,000; and Chile, 8,500. The largest sending agency in the United States is the Church of Jesus Christ of Latter Day Saints who, at this date 2019, has 67,000 full time proselytizing young missionaries all over the world with many more elder missionaries serving in similar circumstances. The Southern Baptist Convention, has 4,800 missionaries, plus 450 support staff working inside the United States. The annual budget is about $50,000 per year per missionary. In recent years, however, the Southern Baptist foreign missionary operation (the International Mission Board) has operated at a deficit, and it is cutting operations by 15 percent. It is encouraging older missionaries to retire and return to the United States.

Modern missionary methods and doctrines among conservative Protestants

The Lausanne Congress of 1974, birthed a movement that supports evangelical mission among non-Christians and nominal Christians. It regards "mission" as that which is designed "to form a viable indigenous church-planting and world changing movement." This definition is motivated by a theologically imperative theme of the Bible to make God known, as outlined in the Great Commission. The definition is claimed to summarize the acts of Jesus' ministry, which is taken as a model motivation for all ministries.

This Christian missionary movement seeks to implement churches after the pattern of the first century Apostles. The process of forming disciples is necessarily social. "Church" should be understood in the widest sense, as a body of believers of Christ rather than simply a building. In this view, even those who are already culturally Christian must be "evangelized".

Church planting by cross-cultural missionaries leads to the establishment of self-governing, self-supporting and self-propagating communities of believers. This is the famous "three-self" formula formulated by Henry Venn of the London Church Missionary Society in the 19th century. Cross-cultural missionaries are persons who accept church-planting duties to evangelize people outside their culture, as Christ commanded in the Great Commission (Matthew 28:18–20, Mark 16:15–18).

The objective of these missionaries is to give an understandable presentation of their beliefs with the hope that people will choose to following the teaching of Jesus Christ and live their lives as His disciples. As a matter of strategy, many evangelical Christians around the world now focus on what they call the "10/40 window", a band of countries between 10 and 40 degrees north latitude and reaching from western Africa through Asia. Christian missions strategist Luis Bush pinpointed the need for a major focus of evangelism in the "10/40 Window", a phrase he coined in his presentation at the missionary conference Lausanne 1989 in Manila. Sometimes referred to as the "Resistant Belt", it is an area that includes 35% of the world's land mass, 90% of the world's poorest peoples and 95% of those who have yet to hear anything about Christianity.

Modern mission techniques are sufficiently refined that within ten to fifteen years, most indigenous churches are locally pastored, managed, taught, self-supporting and evangelizing. The process can be substantially faster if a preexisting translation of the Bible and higher pastoral education are already available, perhaps left over from earlier, less effective missions.

One strategy is to let indigenous cultural groups decide to adopt Christian doctrines and benefits, when (as in most cultures) such major decisions are normally made by groups. In this way, opinion leaders in the groups can persuade much or most of the groups to convert. When combined with training in discipleship, church planting and other modern missionary doctrine, the result is an accelerating, self-propelled conversion of large portions of the culture.

A typical modern mission is a co-operative effort by many different ministries, often including several coordinating ministries, such as the Faith2Share network, often with separate funding sources. One typical effort proceeded as follows:

  1. A missionary radio group recruits, trains and broadcasts in the main dialect of the target culture's language. Broadcast content is carefully adapted to avoid syncretism yet help the Christian Gospel seem like a native, normal part of the target culture. Broadcast content often includes news, music, entertainment and education in the language, as well as purely Christian items.
  2. Broadcasts might advertise programs, inexpensive radios (possibly spring-wound), and a literature ministry that sells a Christian mail-order correspondence course at nominal costs. The literature ministry is key, and is normally a separate organization from the radio ministry. Modern literature missions are shifting to web-based content where it makes sense (as in Western Europe and Japan).
  3. When a person or group completes a correspondence course, they are invited to contact a church-planting missionary group from (if possible) a related cultural group. The church-planting ministry is usually a different ministry from either the literature or radio ministries. The church-planting ministry usually requires its missionaries to be fluent in the target language, and trained in modern church-planting techniques.
  4. The missionary then leads the group to start a church. Churches planted by these groups are usually a group that meets in a house. The object is the minimum organization that can perform the required character development and spiritual growth. Buildings, complex ministries and other expensive items are mentioned, but deprecated until the group naturally achieves the size and budget to afford them. The crucial training is how to become a Christian (by faith in Jesus Christ) and then how to set up a church (meet to study the Bible, and perform communion and worship), usually in that order.
  5. A new generation of churches is created, and the growth begins to accelerate geometrically. Frequently, daughter churches are created only a few months after a church's creation. In the fastest-growing Christian movements, the pastoral education is "pipelined", flowing in a just-in-time fashion from the central churches to daughter churches. That is, planting of churches does not wait for the complete training of pastors.

The most crucial part of church planting is selection and training of leadership. Classically, leadership training required an expensive stay at a seminary, a Bible college. Modern church planters deprecate this because it substantially slows the growth of the church without much immediate benefit. Modern mission doctrines replace the seminary with programmed curricula or (even less expensive) books of discussion questions, and access to real theological books. The materials are usually made available in a major trading language in which most native leaders are likely to be fluent. In some cases, the materials can be adapted for oral use.

It turns out that new pastors' practical needs for theology are well addressed by a combination of practical procedures for church planting, discussion in small groups, and motivated Bible-based study from diverse theological texts. As a culture's church's wealth increases, it will naturally form classic seminaries on its own.

Another related mission is Bible translation. The above-mentioned literature has to be translated. Missionaries actively experiment with advanced linguistic techniques to speed translation and literacy. Bible translation not only speeds a church's growth by aiding self-training, but it also assures that Christian information becomes a permanent part of the native culture and literature. Some ministries also use modern recording techniques to reach groups with audio that could not be soon reached with literature.

Among Roman Catholics

For Catholics, “Missions” is the term given to those particular undertakings by which the heralds of the Gospel, sent out by the Church and going forth into the whole world, carry out the task of preaching the Gospel and planting the Church among peoples or groups who do not yet believe in Christ.

Vatican II made a deep impact on Catholic missions around the world. The Church's relations to non-Christian religions like Judaism and Islam were revisited.

A steep decline in the number of people entering the priesthood and religious life in the West has made the Church look towards laity more and more. Communities like Opus Dei arose to meet this need.

Inculturation increasingly became a key topic of missiological reflection for Catholics. Inculturation is understood as the meeting of the Christian message with a community in their cultural context.

Liberation Theology and liturgical reform have also been important in forming and influencing the mission of the Catholic Church in the 20th and 21st Centuries.

In relation to mission, Pope Benedict XVI made the re-evangelization of Europe and North America a priority in his own ministry, even while the upper leadership of the Roman Catholic hierarchy and the college of cardinals has more members from Latin America, Africa, and Asia than ever before.

Key documents on mission for Catholics during this period are Evangelii nuntiandi by Pope Paul VI and Redemptoris missio by Pope John Paul II.

Print and new media in mission

Christian mission organisations have long depended on the printed word as a channel through which to do mission. At times when countries have been "closed" to Christians, great efforts have been made to smuggle Bibles and other literature into those countries. Brother Andrew, the founder of Open Doors, started smuggling Bibles into communist countries in the 1950s. Operation Mobilisation was established in 1957 by George Verwer. Other Christian publishers, such as Plough Publishing, provide free books to people in the UK and US as a form of mission. The Bible Society translates and prints Bibles, in an attempt to reach every country in the world.

The internet now provides Christian mission organisations a convent way of reaching people in the form of podcasts. Podcasts provide a way of dissemination for a message that has potential to endanger the recipient, since it is very hard to track who has downloaded a specific podcast. An example of this is the Crescent Project. Other podcasts, such as the Life Together podcast, The Sacred, and Harvest are aimed at both non-Christians and Christians in the home country.

Reverse mission

The shift in world Christian population from Europe and North America to the non-Western world, and the migration of Africans, Asians, and Latin Americans to the West has given rise to what some have termed "reverse mission". It demonstrates a reversal of the missionary movement, in that it reverses the direction of earlier missionary efforts.

Inter-Organizational Missions

Globalization of the 21st century has served as a platform for opportunity for independent Christian organizations to unite together in cooperation for outreach missions and discipleship.

Some organizations are Christian consortiums which organizationally band themselves together like 50,000 persons in the Illinois based Missio Nexus organization led by Ted Esler.

Other organizations are united by a common source of financial funding, cooperation in outreach projects and digital communications between internal missions personnel around the world and their partners like the 25,000 people united in the GMNF Global Mission Society, founded by Anton R. Williams of Kalamazoo, Michigan and Grand Rapids, Michigan.

Still other organizations sign legal contacts with an agencies to join together for specific functions in missions like the SIMS organization.

Criticism

In 1924, Mahatma Gandhi wrote:

This [Christian] proselytization will mean no peace in the world. Conversions are harmful to India. If I had the power and could legislate I should certainly stop all proselytizing ... It pains me to have to say that the Christian missionaries as a body, with honorable exceptions, have actively supported a system which has impoverished, enervated and demoralized a people considered to be among the gentlest and most civilized on earth.

In India, Hindu organisations such as the Rashtriya Swayamsevak Sangh assert that most conversions undertaken by zealous evangelicals occur due to compulsion, inducement or fraud. In the Indian state of Tripura, the government has alleged financial and weapons-smuggling connections between Baptist missionaries and rebel groups such as the National Liberation Front of Tripura. The accused Tripura Baptist Christian Union is a member body of the Baptist World Alliance.

In mid-May, the Vatican was also co-sponsoring a meeting about how some religious groups abuse liberties by proselytizing, or by evangelizing in aggressive or deceptive ways. Iraq ... has become an open field for foreigners looking for fresh converts. Some Catholic Church leaders and aid organizations have expressed concern about new Christian groups coming in and luring Iraqis to their churches with offers of cash, clothing, food or jobs. ... Reports of aggressive proselytism and reportedly forced conversions in mostly Hindu India have fueled religious tensions and violence there and have prompted some regional governments to pass laws banning proselytism or religious conversion. ... Sadhvi Vrnda Chaitanya, a Hindu monk from southern India, told CNS that India's poor and uneducated are especially vulnerable to coercive or deceptive methods of evangelization. ... Aid work must not hide any ulterior motives and avoid exploiting vulnerable people like children and the disabled, she said.

In an interview with Outlook magazine, Sadhvi Vrnda Chaitanya said "If the Vatican could understand that every religious and spiritual tradition is as sacred as Christianity, and that they have a right to exist without being denigrated or extinguished, it will greatly serve the interests of dialogue, mutual respect, and peaceful coexistence."

Communicating diseases

European explorers in the Americas introduced Afro-Eurasian diseases to which Amerindian peoples had no immunity, leading to tens of millions of deaths. Missionaries, along with other travelers, brought diseases into native populations. Smallpox, measles, and common cold, have been blamed on their arrivals. David Igler of the University of California, Irvine, includes missionary activity as a cause of spreading germs. However, he says that commercial traders were the main agents of disease:

other diseases arrived on non-commercial voyages; missionary activities certainly spread germs, and Spanish conquests had dispersed deadly germs in parts of the Americas and Pacific prior to the late eighteenth century. Yet, for the period between the 1770s and the 1840s, trading vessels were the main agents of disease, creating in the Pacific what Emmanuel Le Roy Ladurie has called a "paroxysm" of the "microbian unification of the world." By 1850, the microbes of Europe, Asia, and Africa circulated in almost every Pacific population.

Aid and evangelism

While there is a general agreement among most major aid organizations not to mix aid with proselyting, others see disasters as a useful opportunity to spread the word. One such an occurrence was the tsunami that devastated parts of Asia on December 26, 2004.

"This (disaster) is one of the greatest opportunities God has given us to share his love with people," said K.P. Yohannan, president of the Texas-based Gospel for Asia. In an interview, Yohannan said his 14,500 "native missionaries" in India, Sri Lanka and the Andaman Islands are giving survivors Bibles and booklets about "how to find hope in this time through the word of God." In Krabi, Thailand, a Southern Baptist church had been "praying for a way to make inroads" with a particular ethnic group of fishermen, according to Southern Baptist relief coordinator Pat Julian. Then came the tsunami, "a phenomenal opportunity" to provide ministry and care, Julian told the Baptist Press news service. ... Not all evangelicals agree with these tactics. "It's not appropriate in a crisis like this to take advantage of people who are hurting and suffering", said the Rev. Franklin Graham, head of Samaritan's Purse and son of evangelist Billy Graham.

The Christian Science Monitor echoes these concerns: "'I think evangelists do this out of the best intentions, but there is a responsibility to try to understand other faith groups and their culture,' says Vince Isner, director of FaithfulAmerica.org, a program of the National Council of Churches USA."

The Bush administration has made it easier for U.S. faith-based groups and missionary societies to tie aid and church together.

For decades, US policy has sought to avoid intermingling government programs and religious proselytizing. The aim is both to abide by the Constitution's prohibition against a state religion and to ensure that aid recipients don't forgo assistance because they don't share the religion of the provider. ... But many of those restrictions were removed by Bush in a little-noticed series of executive orders – a policy change that cleared the way for religious groups to obtain hundreds of millions of dollars in additional government funding. It also helped change the message American aid workers bring to many corners of the world, from emphasizing religious neutrality to touting the healing powers of the Christian God.

Christian counter-claims

Missionaries say that the government in India has passed anti-conversion laws in several states that are supposedly meant to prevent conversions from "force or allurement", but are primarily used, they say, to persecute and criminalize voluntary conversion due to the government's broad definition of "force and allurement". Any gift received from a Christian in exchange for, or with the intention of, conversion is considered allurement. Voice of the Martyrs reports that aid-workers claim that they are being hindered from reaching people with much needed services as a result of this persecution. Alan de Lastic, Roman Catholic archbishop of New Delhi states that claims of forced conversion are false.

"'There are attacks practically every week, maybe not resulting in death, but still, violent attacks,' Richard Howell, general secretary of the Evangelical Fellowship of India tells The Christian Science Monitor today. 'They [India's controlling BJP party] have created an atmosphere where minorities do feel insecure.'" According to Prakash Louis, director of the secular Indian Social Institute in New Delhi, "We are seeing a broad attempt to stifle religious minorities and their constitutional rights ... Today, they say you have no right to convert, Tomorrow you have no right to worship in certain places." Existing congregations, often during times of worship, are being persecuted. Properties are sometimes destroyed and burnt to the ground, while native pastors are sometimes beaten and left for dead.

Political scientist Robert Woodberry claims that conversionary Protestants were a crucial catalyst in spreading religious liberty, education, and democracy. While his historical analysis is exhaustive, the accompanying empirical evidence suffers from severe inconsistencies. Elena Nikolova and Jakub Polansky replicate Woodberry's analysis using twenty-six alternative democracy measures and extend the time period over which the democracy measures are averaged. These two simple modifications lead to the breakdown of Woodberry's results. Overall, no significant relationship between Protestant missions and the development of democracy can be established.

A major contribution of the Christian missionaries in Africa, China, Guatemala, India, Indonesia, Korea, and other places was better health care of the people through hygiene and introducing and distributing soap, and "cleanliness and hygiene became an important marker of being identified as a Christian".

Nomenclature

From Wikipedia, the free encyclopedia

Nomenclature (UK: /nəˈmɛŋkləɜːr/, US: /ˈnmənklər/) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. The principles of naming vary from the relatively informal conventions of everyday speech to the internationally agreed principles, rules and recommendations that govern the formation and use of the specialist terminology used in scientific and any other disciplines.

Naming "things" is a part of general human communication using words and language: it is an aspect of everyday taxonomy as people distinguish the objects of their experience, together with their similarities and differences, which observers identify, name and classify. The use of names, as the many different kinds of nouns embedded in different languages, connects nomenclature to theoretical linguistics, while the way humans mentally structure the world in relation to word meanings and experience relates to the philosophy of language.

Onomastics, the study of proper names and their origins, includes: anthroponymy (concerned with human names, including personal names, surnames and nicknames); toponymy (the study of place names); and etymology (the derivation, history and use of names) as revealed through comparative and descriptive linguistics.

The scientific need for simple, stable and internationally accepted systems for naming objects of the natural world has generated many formal nomenclatural systems.[citation needed] Probably the best known of these nomenclatural systems are the five codes of biological nomenclature that govern the Latinized scientific names of organisms.

Etymology

The word nomenclature is derived from the Latin nomen ('name'), and calare ('to call'). The Latin term nomenclatura refers to a list of names, as does the word nomenclator, which can also indicate a provider or announcer of names.

Onomastics and nomenclature

The study of proper names is known as onomastics, which has a wide-ranging scope that encompasses all names, languages, and geographical regions, as well as cultural areas.

The distinction between onomastics and nomenclature is not readily clear: onomastics is an unfamiliar discipline to most people, and the use of nomenclature in an academic sense is also not commonly known. Although the two fields integrate, nomenclature concerns itself more with the rules and conventions that are used for the formation of names.

Influence of social, political, religious factors

Due to social, political, religious, and cultural motivations, things that are the same may be given different names, while different things may be given the same name; closely related similar things may be considered separate, while on the other hand significantly different things might be considered the same.

For example, Hindi and Urdu are both closely related, mutually intelligible Hindustani languages (one being sanskritised and the other arabised). However, they are favored as separate languages by Hindus and Muslims respectively, as seen in the context of Hindu-Muslim conflict resulting in the violence of the 1947 Partition of India. In contrast, mutually unintelligible dialects that differ considerably in structure, such as Moroccan Arabic, Yemeni Arabic, and Lebanese Arabic, are considered to be the same language due to the pan-Islamism religious identity.

Cultural nomenclature

Names provide us with a way of structuring and mapping the world in our minds so, in some way, they mirror or represent the objects of our experience.

Names, words, language, meaning

Elucidating the connections between language (especially names and nouns), meaning, and the way we perceive the world has provided a rich field of study for philosophers and linguists. Relevant areas of study include: the distinction between proper names and proper nouns; as well as the relationship between names, their referents, meanings (semantics), and the structure of language.

Folk taxonomy

Modern scientific taxonomy has been described as "basically a Renaissance codification of folk taxonomic principles." Formal systems of scientific nomenclature and classification are exemplified by biological classification. All classification systems are established for a purpose. The scientific classification system anchors each organism within the nested hierarchy of internationally accepted classification categories. Maintenance of this system involves formal rules of nomenclature and periodic international meetings of review. This modern system evolved from the folk taxonomy of prehistory.

Folk taxonomy can be illustrated through the Western tradition of horticulture and gardening. Unlike scientific taxonomy, folk taxonomies serve many purposes. Examples in horticulture would be the grouping of plants, and naming of these groups, according to their properties and uses:

Folk taxonomy is generally associated with the way rural or indigenous peoples use language to make sense of and organise the objects around them. Ethnobiology frames this interpretation through either "utilitarianists" like Bronislaw Malinowski who maintain that names and classifications reflect mainly material concerns, and "intellectualists" like Claude Lévi-Strauss who hold that they spring from innate mental processes. The literature of ethnobiological classifications was reviewed in 2006. Folk classification is defined by the way in which members of a language community name and categorize plants and animals whereas ethnotaxonomy refers to the hierarchical structure, organic content, and cultural function of biological classification that ethnobiologists find in every society around the world.

Ethnographic studies of the naming and classification of animals and plants in non-Western societies have revealed some general principles that suggest pre-scientific man's conceptual and linguistic method of organising the biological world in a hierarchical way. Such studies indicate that the urge to classify is a basic human instinct.

  • in all languages natural groups of organisms are distinguished (present-day taxa)
  • these groups are arranged into more inclusive groups or ethnobiological categories
  • in all languages there are about five or six ethnobiological categories of graded inclusiveness
  • these groups (ethnobiological categories) are arranged hierarchically, generally into mutually exclusive ranks
  • the ranks at which particular organisms are named and classified is often similar in different cultures

The levels, moving from the most to least inclusive, are:

  1. "unique beginner" — e.g. plant or animal. A single all-inclusive name rarely used in folk taxonomies but loosely equivalent to an original living thing, a "common ancestor"
  2. "life form" — e.g. tree, bird, grass and fish. These are usually primary lexemes (basic linguistic units) loosely equivalent to a phylum or major biological division.
  3. "generic name" — e.g. oak, pine, robin, catfish. This is the most numerous and basic building block of all folk taxonomies, the most frequently referred to, the most important psychologically, and among the first learned by children. These names can usually be associated directly with a second level group. Like life-form names these are primary lexemes.
  4. "specific name" — e.g. white fir, post oak. More or less equivalent to species. A secondary lexeme and generally less frequent than generic names.
  5. "varietal name" — e.g. baby lima bean, butter lima bean.

In almost all cultures objects are named using one or two words equivalent to 'kind' (genus) and 'particular kind' (species). When made up of two words (a binomial) the name usually consists of a noun (like salt, dog or star) and an adjectival second word that helps describe the first, and therefore makes the name, as a whole, more "specific", for example, lap dog, sea salt, or film star. The meaning of the noun used for a common name may have been lost or forgotten (whelk, elm, lion, shark, pig) but when the common name is extended to two or more words much more is conveyed about the organism's use, appearance or other special properties (sting ray, poison apple, giant stinking hogweed, hammerhead shark). These noun-adjective binomials are just like our own names with a family or surname like Simpson and another adjectival Christian or forename name that specifies which Simpson, say Homer Simpson. It seems reasonable to assume that the form of scientific names we call binomial nomenclature is derived from this simple and practical way of constructing common names—but with the use of Latin as a universal language.

In keeping with the utilitarian view other authors maintain that ethnotaxonomies resemble more a "complex web of resemblances" than a neat hierarchy. Likewise, a recent study has suggested that some folk taxonomies display more than six ethnobiological categories. Others go further and even doubt the reality of such categories, especially those above the generic name level.

Names and nouns

A name is a label for any noun: names can identify a class or category of things; or a single thing, either uniquely or within a given context. Names are given, for example, to humans or any other organisms, places, products—as in brand names—and even to ideas or concepts. It is names as nouns that are the building blocks of nomenclature.

The word name is possibly derived from the Proto-Indo-European language hypothesised word nomn. The distinction between names and nouns, if made at all, is extremely subtle, although clearly noun refers to names as lexical categories and their function within the context of language, rather that as "labels" for objects and properties.

Personal names

Human personal names, also referred to as prosoponyms, are presented, used and categorised in many ways depending on the language and culture. In most cultures (Indonesia is one exception) it is customary for individuals to be given at least two names. In Western culture, the first name is given at birth or shortly thereafter and is referred to as the given name, the forename, the baptismal name (if given then), or simply the first name. In England prior to the Norman invasion of 1066, small communities of Celts, Anglo-Saxons and Scandinavians generally used single names: each person was identified by a single name as either a personal name or nickname. As the population increased, it gradually became necessary to identify people further—giving rise to names like John the butcher, Henry from Sutton, and Roger son of Richard...which naturally evolved into John Butcher, Henry Sutton, and Roger Richardson. We now know this additional name variously as the second name, last name, family name, surname or occasionally the byname, and this natural tendency was accelerated by the Norman tradition of using surnames that were fixed and hereditary within individual families. In combination these two names are now known as the personal name or, simply, the name. There are many exceptions to this general rule: Westerners often insert a third or more names between the given and surnames; Chinese and Hungarian names have the family name preceding the given name; females now often retain their maiden names (their family surname) or combine, using a hyphen, their maiden name and the surname of their husband; some East Slavic nations insert the patronym (a name derived from the given name of the father) between the given and the family name; in Iceland the given name is used with the patronym, or matronym (a name derived from the given name of the mother), and surnames are rarely used. Nicknames (sometimes called hypocoristic names) are informal names used mostly between friends.

Common names and proper names

The distinction between proper names and common names is that proper names denote a unique entity e.g. London Bridge, while common names are used in a more general sense in reference to a class of objects e.g. bridge. Many proper names are obscure in meaning as they lack any apparent meaning in the way that ordinary words mean, probably for the practical reason that when they consist of Collective nouns, they refer to groups, even when they are inflected for the singular e.g. "committee". Concrete nouns like "cabbage" refer to physical bodies that can be observed by at least one of the senses while abstract nouns, like "love" and "hate" refer to abstract objects. In English, many abstract nouns are formed by adding noun-forming suffixes ('-ness', '-ity', '-tion') to adjectives or verbs e.g. "happiness", "serenity", "concentration." Pronouns like "he", "it", "which", and "those" stand in place of nouns in noun phrases.

The capitalization of nouns varies with language and even the particular context: journals often have their own house styles for common names.

-onym nouns

Distinctions may be made between particular kinds of names simply by using the suffix -onym, from the Greek ónoma (ὄνομα, 'name'). So we have, for example, hydronyms name bodies of water, synonyms are names with the same meaning, and so on. The entire field could be described as chrematonymy—the names of things.

Toponyms

Toponyms are proper names given to various geographical features (geonyms), and also to cosmic features (cosmonyms). This could include names of mountains, rivers, seas, villages, towns, cities, countries, planets, stars etc. Toponymy can be further divided into specialist branches, like: choronymy, the study of proper names of regions and countries; econymy, the study of proper names of villages, towns and citties; hodonymy, the study of proper names of streets and roads; hydronymy, the study of proper names of water bodies; oronymy, the study of proper names of mountains and hills, etc.

Toponymy has popular appeal because of its socio-cultural and historical interest and significance for cartography. However, work on the etymology of toponyms has found that many place names are descriptive, honorific or commemorative but frequently they have no meaning, or the meaning is obscure or lost. Also, the many categories of names are frequently interrelated. For example, many place-names are derived from personal names (Victoria), many names of planets and stars are derived from the names of mythological characters (Venus, Neptune), and many personal names are derived from place-names, names of nations and the like (Wood, Bridge).

Scientific nomenclature

Nomenclature, classification, identification

In a strictly scientific sense, nomenclature is regarded as a part of taxonomy (though distinct from it). Moreover, the precision demanded by science in the accurate naming of objects in the natural world has resulted in a variety of codes of nomenclature (worldwide-accepted sets of rules on biological classification).

Taxonomy can be defined as the study of classification including its principles, procedures and rules, while classification itself is the ordering of taxa (the objects of classification) into groups based on similarities or differences. Doing taxonomy entails identifying, describing, and naming taxa; therefore, in the scientific sense, nomenclature is the branch of taxonomy concerned with the application of scientific names to taxa, based on a particular classification scheme, in accordance with agreed international rules and conventions.

Identification determines whether a particular organism matches a taxon that has already been classified and named – so classification must precede identification. This procedure is sometimes referred to as determination.

Biology

Although Linnaeus' system of binomial nomenclature was rapidly adopted after the publication of his Species Plantarum and Systema Naturae in 1753 and 1758 respectively, it was a long time before there was international consensus concerning the more general rules governing biological nomenclature. The first botanical code was produced in 1905, the zoological code in 1889 and cultivated plant code in 1953. Agreement on the nomenclature and symbols for genes emerged in 1979.

Astronomy

Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered every year. Astronomers need universal systematic designations to unambiguously identify all of these objects using astronomical naming conventions, while assigning names to the most interesting objects and, where relevant, naming important or interesting features of those objects.

Chemistry

The IUPAC nomenclature is a system of naming chemical compounds and for describing the science of chemistry in general. It is maintained by the International Union of Pure and Applied Chemistry.

Similar compendia exist for biochemistry (in association with the IUBMB), analytical chemistry and macromolecular chemistry. These books are supplemented by shorter recommendations for specific circumstances which are published from time to time in the journal Pure and Applied Chemistry. These systems can be accessed through the International Union of Pure and Applied Chemistry (IUPAC).

Other sciences

Single crystal

From Wikipedia, the free encyclopedia

In materials science, a single crystal (or single-crystal solid or monocrystalline solid) is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries. The absence of the defects associated with grain boundaries can give monocrystals unique properties, particularly mechanical, optical and electrical, which can also be anisotropic, depending on the type of crystallographic structure. These properties, in addition to making some gems precious, are industrially used in technological applications, especially in optics and electronics.

Because entropic effects favor the presence of some imperfections in the microstructure of solids, such as impurities, inhomogeneous strain and crystallographic defects such as dislocations, perfect single crystals of meaningful size are exceedingly rare in nature. The necessary laboratory conditions often add to the cost of production. On the other hand, imperfect single crystals can reach enormous sizes in nature: several mineral species such as beryl, gypsum and feldspars are known to have produced crystals several meters across.

The opposite of a single crystal is an amorphous structure where the atomic position is limited to short-range order only. In between the two extremes exist polycrystalline, which is made up of a number of smaller crystals known as crystallites, and paracrystalline phases. Single crystals will usually have distinctive plane faces and some symmetry, where the angles between the faces will dictate its ideal shape. Gemstones are often single crystals artificially cut along crystallographic planes to take advantage of refractive and reflective properties.

Production methods

Although current methods are extremely sophisticated with modern technology, the origins of crystal growth can be traced back to salt purification by crystallization in 2500 BCE. A more advanced method using an aqueous solution was started in 1600 CE while the melt and vapor methods began around 1850 CE.

Single-crystal growth methods tree diagram

Basic crystal growth methods can be separated into four categories based on what they are artificially grown from: melt, solid, vapor, and solution. Specific techniques to produce large single crystals (aka boules) include the Czochralski process (CZ), Floating zone (or Zone Movement), and the Bridgman technique. Dr. Teal and Dr. Little of Bell Telephone Laboratories were the first to use the Czochralski method to create Ge and Si single crystals. Other methods of crystallization may be used, depending on the physical properties of the substance, including hydrothermal synthesis, sublimation, or simply solvent-based crystallization. For example, a modified Kyropoulos method can be used to grow high quality 300 kg sapphire single crystals. The Verneuil method, also called the flame-fusion method, was used in the early 1900s to make rubies before CZ. The diagram on the right illustrates most of the conventional methods. There have been new breakthroughs such as chemical vapor depositions (CVD) along with different variations and tweaks to the existing methods. These are not shown in the diagram.

A single-crystal quartz bar grown by the hydrothermal method

In the case of metal single crystals, fabrication techniques also include epitaxy and abnormal grain growth in solids. Epitaxy is used to deposit very thin (micrometer to nanometer scale) layers of the same or different materials on the surface of an existing single crystal. Applications of this technique lie in the areas of semiconductor production, with potential uses in other nanotechnological fields and catalysis.

It is extremely difficult to grow single crystals of the polymers. It is mainly because that the polymer chains are of different length and due to the various entropy reasons. However, topochemical reactions are one of the easy methods to get single crystals of the polymer.

Applications

Semiconductor industry

One of the most used single crystals is that of Silicon in the semiconductor industry. The four main production methods for semiconductor single crystals are from metallic solutions: liquid phase epitaxy (LPE), liquid phase electroepitaxy (LPEE), the traveling heater method (THM), and liquid phase diffusion (LPD). However, there are many other single crystals besides inorganic single crystals capable semiconducting, including single-crystal organic semiconductors.

A high-purity (99.999 %) tantalum single crystal, made by the floating zone process, some single crystalline fragments of tantalum, and a high-purity (99.99% = 4N) 1 cm3 tantalum cube for comparison. This photo was taken by Alchemist-hp.

Monocrystalline silicon used in the fabrication of semiconductors and photovoltaics is the greatest use of single-crystal technology today. In photovoltaics, the most efficient crystal structure will yield the highest light-to-electricity conversion. On the quantum scale that microprocessors operate on, the presence of grain boundaries would have a significant impact on the functionality of field effect transistors by altering local electrical properties. Therefore, microprocessor fabricators have invested heavily in facilities to produce large single crystals of silicon. The Czochralski method and floating zone are popular methods for the growth of Silicon crystals.

Other inorganic semiconducting single crystals include GaAs, GaP, GaSb, Ge, InAs, InP, InSb, CdS, CdSe, CdTe, ZnS, ZnSe, and ZnTe. Most of these can also be tuned with various doping for desired properties. Single-crystal graphene is also highly desired for applications in electronics and optoelectronics with its large carrier mobility and high thermal conductivity, and remains a topic of fervent research. One of the main challenges has been growing uniform single crystals of bilayer or multilayer graphene over large areas; epitaxial growth and the new CVD (mentioned above) are among the new promising methods under investigation.

Organic semiconducting single crystals are different from the inorganic crystals. The weak intermolecular bonds mean lower melting temperatures, and higher vapor pressures and greater solubility. For single crystals to grow, the purity of the material is crucial and the production of organic materials usually require many steps to reach the necessary purity. Extensive research is being done to look for materials that are thermally stable with high charge-carrier mobility. Past discoveries include naphthalene, tetracene, and 9,10-diphenylanthacene (DPA). Triphenylamine derivatives have shown promise, and recently in 2021, the single-crystal structure of α-phenyl-4′-(diphenylamino)stilbene (TPA) grown using the solution method exhibited even greater potential for semiconductor use with its anisotropic hole transport property.

Optical application

A huge KDP, potassium dihydrogen phosphate, crystal grown from a seed crystal in a supersaturated aqueous solution at LLNL which is to be cut into slices and used on the National Ignition Facility for frequency doubling and tripling.

Single crystals have unique physical properties due to being a single grain with molecules in a strict order and no grain boundaries. This includes optical properties, and single crystals of silicon is also used as optical windows because of its transparency at specific infrared (IR) wavelengths, making it very useful for some instruments.

Sapphires: Better known as the alpha phase of aluminum oxide (Al2O3) by scientists, sapphire single crystals are widely used in hi-tech engineering. It can be grown from gaseous, solid, or solution phases. The diameter of the crystals resulting from the growth method are important when considering electronic uses after. They are used for lasers and nonlinear optics. Some notable uses are as in the window of a biometric fingerprint reader, optical disks for long-term data storage, and X-ray interferometer.

Indium Phosphide: These single crystals are particularly appropriate for combining optoelectronics with high-speed electronics in the form of optical fiber with its large-diameter substrates. Other photonic devices include lasers, photodetectors, avalanche photo diodes, optical modulators and amplifiers, signal processing, and both optoelectronic and photonic integrated circuits.

Aluminum oxide crystals

Germanium: This was the material in the first transistor invented by Bardeen, Brattain, and Shockley in 1947. It is used in some gamma-ray detectors and infrared optics. Now it has become the focus of ultrafast electronic devices for its intrinsic carrier mobility.

Arsenide: Arsenide III can be combined with various elements such as B, Al, Ga, and In, with the GaAs compound being in high demand for wafers.

Cadmium Telluride: CdTe crystals have several applications as substrates for IR imaging, electrooptic devices, and solar cells. By alloying CdTe and ZnTe together room-temperature X-ray and gamma-ray detectors can be made.

Electrical conductors

Metals can surprisingly be produced in single-crystal form and provide a means to understand the ultimate performance of metallic conductors. It is vital for understanding the basic science such as catalytic chemistry, surface physics, electrons, and monochromators. Production of metallic single crystals have the highest quality requirements and are grown, or pulled, in the form of rods. Certain companies can produce specific geometries, grooves, holes, and reference faces along with varying diameters.

Of all the metallic elements, silver and copper have the best conductivity at room temperature, setting the bar for performance. The size of the market, and vagaries in supply and cost, have provided strong incentives to seek alternatives or find ways to use less of them by improving performance.

The conductivity of commercial conductors is often expressed relative to the International Annealed Copper Standard, according to which the purest copper wire available in 1914 measured around 100%. The purest modern copper wire is a better conductor, measuring over 103% on this scale. The gains are from two sources. First, modern copper is more pure. However, this avenue for improvement seems at an end. Making the copper purer still makes no significant improvement. Second, annealing and other processes have been improved. Annealing reduces the dislocations and other crystal defects which are sources of resistance. But the resulting wires are still polycrystalline. The grain boundaries and remaining crystal defects are responsible for some residual resistance. This can be quantified and better understood by examining single crystals.

As anticipated, single-crystal copper did prove to have better conductivity than polycrystalline copper.

Electrical resistivity ρ for silver (Ag) / copper (Cu) materials at room temperature (293 K) 
Material ρ (μΩ∙cm) IACS
Single-crystal Ag, doped with 3 mol% Cu 1.35 127%
Single-crystal Cu, further processed 1.472 117.1%
Single-crystal Ag 1.49 115.4%
Single-crystal Cu 1.52 113.4%
High-purity Ag wire (polycrystalline) 1.59 108%
High-purity Cu wire (polycrystalline) 1.67 ˃ 103%

However, the single-crystal copper not only became a better conductor than high purity polycrystalline silver, but with prescribed heat and pressure treatment could surpass even single-crystal silver. Although impurities are usually bad for conductivity, a silver single crystal with a small amount of copper substitutions proved to be the best.

As of 2009, no single-crystal copper is manufactured on a large scale industrially, but methods of producing very large individual crystal sizes for copper conductors are exploited for high performance electrical applications. These can be considered meta-single crystals with only a few crystals per meter of length.

Pigtail from single-crystal blade casting

Single-crystal turbine blades

Another application of single-crystal solids is in materials science in the production of high strength materials with low thermal creep, such as turbine blades. Here, the absence of grain boundaries actually gives a decrease in yield strength, but more importantly decreases the amount of creep which is critical for high temperature, close tolerance part applications. Researcher Barry Piearcey found that a right-angle bend at the casting mold would decrease the number of columnar crystals and later, scientist Giamei used this to start the single-crystal structure of the turbine blade.

In research

Single crystals are essential in research especially condensed-matter physics and all aspects of materials science such as surface science. The detailed study of the crystal structure of a material by techniques such as Bragg diffraction and helium atom scattering is easier with single crystals because it is possible to study directional dependence of various properties and compare with theoretical predictions. Furthermore, macroscopically averaging techniques such as angle-resolved photoemission spectroscopy or low-energy electron diffraction are only possible or meaningful on surfaces of single crystals. In superconductivity there have been cases of materials where superconductivity is only seen in single-crystalline specimen. They may be grown for this purpose, even when the material is otherwise only needed in polycrystalline form.

As such, numerous new materials are being studied in their single-crystal form. The young field of metal-organic-frameworks (MOFs) is one of many which qualify to have single crystals. In January 2021 Dr. Dong and Dr. Feng demonstrated how polycyclic aromatic ligands can be optimized to produce large 2D MOF single crystals of sizes up to 200 μm. This could mean scientists can fabricate single-crystal devices and determine intrinsic electrical conductivity and charge transport mechanism.

The field of photodriven transformation can also be involved with single crystals with something called single-crystal-to-single-crystal (SCSC) transformations. These provide direct observation of molecular movement and understanding of mechanistic details. This photoswitching behavior has also been observed in cutting-edge research on intrinsically non-photo-responsive mononuclear lanthanide single-molecule-magnets (SMM).

Equality (mathematics)

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Equality_...