The history of the rare earths

Rare earth. If you type the first letter of “rare” in , the Google search engine, the term “rare earths” directly appears first on the list of the most-searched terms. What are the backgrounds of these rare-earth “hysteria”? The often used abbreviated name of “rare earths” instead of the metals of the rare earth is misleading. The group's name comes from the time of the discovery of these elements and is based on the fact, that they first found in rare minerals and from these in the form of oxides (before, "earth" called) were isolated. Nur Promethium, a short-lived radioactive element, is really rare in the Earth's crust.

Some of the rare earth metals (Heaven, Yttrium and neodymium) are more common in the earth's crust as for example lead, Molybdenum or arsenic. Thulium, the rarest stable rare earth element, is still more abundant than gold or platinum. The term rare earth metals is appropriate since, than larger deposits of suitable minerals rare indeed. The elements are usually only in small quantities each, in many, widely scattered and overlying minerals present as impurities in other minerals. Much of the industrial production of rare earth metals is done so as a byproduct of the chemical processing in the production of other, concentrated more metals from their ores present.

The similarity of the chemical properties of the rare earth metals makes their separation consuming and costly. Often it is sufficient, interfere inexpensive mischmetal. Of particular interest are the spectroscopic properties of rare earths. So they have in the solid state, For example, in contrast to semiconductors, a discrete energy spectrum. This is due to the particular structure of the electron shell. Optical transitions take place within the 4f shell, that occupied by the larger-5s, 5p- and 6s shells to the outside is shielded from. A band structure can not form the basis of this screening for the f-orbitals. The absorption lines are, due to the individual for the ions of different elements in the crystal electronic environment (Crystal field) exposed. The inhomogeneous line width is sufficient, depending on the crystal, of a few hundred gigahertz up to about ten gigahertz. In the atomic state, most of these transitions, however prohibited. In the solid state the crystal field lifts these atomic transitions by other prohibitions, however, to some extent on. The transition probabilities are still gering.setzen. It is a mixture of rare earth metals, used in the preparation of rare earth ores, For example, monazite, obtained.

China produces more than 90 Percent of the rare earth or rare earth metals worldwide. Hide behind the term itself 17 chemical elements, in hybrid cars, Lamps and many other high-tech products are used. The procedure that the Chinese government in Beijing recently to promote such metals from mines and has imposed export restrictions, led to chaos in some markets. Japan and the United States, the world's largest importers of rare earths, Therefore, China has repeatedly expressed concerns over. Meanwhile, the complaints are piling up of representatives from industry, the use of rare earths. 2010 China cut down the export of rare earths as early as 40 Percent and stopped the delivery of such metals to Japan during a political debate, even temporarily very. This year, prices for rare earths though already risen significantly, but the recent jump in prices has stunned even Chinese analysts.

Johan Gadolin 05.06.1760 -15.08.1852

The story of the year 1787 Carl Axel Arrhenius discovered, a lieutenant in the Swedish Army, an unusual specimen of the black ore close at Feldspatmine Ytterby.[1] 1794 Johan isolated Gadolin, a Finnish professor at the University of Turku, as. 38 % a new, not previously described "earth" (Oxide). Although the Arrhenius mineral was named Ytterite, Anders Gustaf Ekeberg described it as gadolinite. Shortly after, in 1803, isolated by the German chemist Martin Heinrich Klaproth and Jöns Jakob Berzelius and Wilhelm von Hisinger in Sweden independently a similar "Earth" from an ore, the 1751 Axel Frederic Cronstedt had found in a mine near Bastnäs in Sweden. This mineral was named Cerit and the metal cerium, according to the then newly discovered asteroid Ceres. Carl Gustav Mosander, a Swedish surgeon, Chemist and mineralogist, conducted between 1839 and 1841 Experiments on thermal decomposition of a

Carl Gustav Mosander 10.09.1797 - 15.10.1858

Sample from nitrate, which was obtained from Cerit, by. He sapped the product with dilute nitric acid, identified the product as an insoluble cerium oxide and eventually won two new "earth" from the solution, Lanthana (to hide) and Didymia (Twin brother of Lanthana). Similarly, isolated Mosander 1843 three fractions from the initial yttrium oxide: A white (Yttriumoxid), a yellow (Erbium) and a pink (old: Terbiumoxid). These observations led to a period of intensive research into both of cerium oxide and yttrium oxide 1900s until well into the years, involved in the major researchers of that time were. There was duplication of effort, inaccurate reports, dubious discovery claims, and countless examples of confusion due to lack of communication facilities and lack of characterization- and separation methods. Given the existing methods can arise only admiration for the former ingenuity and perseverance of the scientists. After 1850 spectroscopy was used to the newly discovered, detect the presence of known elements and identify new. 1864 nutzte Marc Delafontaine, A Swiss-American chemist, the method, um Yttrium, Terbium and erbium clearly demonstrated as elements. He mistook it the name of terbium and erbium, remained the same today. 1885 started by Carl Auer

Baron Carl Auer von Welsbach, 01.09.1858-04.08.1929

Welsbach with studies of didymium. At the time, was already suspected, that it is at this did not constitute a single element. However, the efforts so far, to separate the individual elements, not been successful. Auer turned it on its method of fractional crystallization, instead of a fractional precipitation. This he succeeded in separating the putative Didyms in praseodymium and neodymium. 1907 He published experimental results on the existence of two elements in ytterbium, which he called aldebaranium and Cassiopeium. After the longest priority dispute in the history of chemistry with the French chemist Georges Urbain they are now called ytterbium and lutetium. With lutetium was the chapter on the history of the discovery of naturally occurring rare earth metals, which had lasted for more than a century, completed. Although all naturally occurring rare earth metals were discovered, This was the then

Georges Urbain 12.04.172 - 05.11.1938

Researchers are not aware. Such as way as both Auer and Urbain continued their work. The theoretical explanation for the similarity of the properties of rare earth metals and also the maximum number of these came later with the development of atomic theory. The atomic number is 1912 introduced by van den Broek. Henry and Henry Moseley discovered Growyn 1913, that there is a mathematically representable relationship between the ordinal number of an element and the frequency of the emitted x-rays at an anti-cathode of the same. Urbain then submitted all the rare earth elements, which recently had been discovered, the test and confirmed by Moseley, that they were real elements. The range of rare earth elements from lanthanum of atomic number 57 to lutetium with 71 was placed. The number 61 was not yet known. 1941 Researchers at the University of Ohio irradiated praseodymium, Neodymium and samarium with neutrons, Deuterons and alpha particles generated by new and radioactivities, The most likely due to the element number 61 were due. The formation of elemental 61 was also 1942 claimed by Wu and Segre. The chemical substance was detected 1945 Clinton Laboratory am, the later Oak Ridge National Laboratory by Marinsky, Glendenin and Coryell, the element by ion exchange chromatography from the products of nuclear fission of uranium and the neutron bombardment of neodymium isolated. They named the new element promethium.[2] In the 1960- 1990s contributed to Roy Allan Mackintosh decisive contributions to the nuclear- and solid state physics understanding of the rare earth group.

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