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Aurivillius Phases
Aurivillius phases are a form of perovskite represented by the general formulae is ( Bi2 O2)(A''n''−1B''n''O3''n''+1) (where A is a large 12 co-ordinate cation, and B is a small 6 co-ordinate cation). Basically, their structure is built by alternating layers of i2O2sup>2+ and pseudo-perovskite blocks, with perovskite layers that are ''n'' octahedral layers in thickness. This crystal structure was first described in 1949 by Swedish chemist Bengt Aurivillius. The first interest in Aurivillius phases arose from the observation of ferroelectricity even for the simplest member, Bi2WO6 (n=1) of this crystallographic family. The Mo-homologous Aurivillius phase Bi2MoO6 was recently investigated as a potential LTCC material. Their oxide ion-conducting properties of Aurivillius phases were first discovered in the 1970s by Takahashi et al., and they have been used too for this purpose ever since. Aurivillius phase oxide materials are a class of lead-free ceramics. See also * Ruddlesde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perovskite
Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as (XIIA2+VIB4+X2−3), known as the perovskite structure. Many different cations can be embedded in this structure, allowing the development of diverse engineered materials. History The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist Lev Perovski (1792–1856). Perovskite's notable crystal structure was first described by Victor Goldschmidt in 1926 in his work on tolerance factors. The crystal structure was later published in 1945 from X-ray diffraction data on barium titanate by Helen Dick Megaw. Occurrence Found in the Earth's mantle, perovskite's occurrence at Khibina Massif is restricted to the silica under-saturated ultramafic rocks and foidolites, due to the instability in a paragenesis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bismuth
Bismuth is a chemical element with the Symbol (chemistry), symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs naturally, and its sulfide and oxide forms are important commercial ores. The free element is 86% as dense as lead. It is a brittle metal with a silvery-white color when freshly produced. Passivation (chemistry), Surface oxidation generally gives samples of the metal a somewhat rosy cast. Further oxidation under heat can give bismuth a vividly Iridescence, iridescent appearance due to thin-film interference. Bismuth is both the most Diamagnetism, diamagnetic element and one of the least Thermal conductivity, thermally conductive metals known. Bismuth was long considered the element with the highest atomic mass whose nuclei do not spontaneously decay. However, in 2003 it was discovered to be extremely weakly radioactive. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is Earth's most abundant element, and after hydrogen and helium, it is the third-most abundant element in the universe. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula . Diatomic oxygen gas currently constitutes 20.95% of the Earth's atmosphere, though this has changed considerably over long periods of time. Oxygen makes up almost half of the Earth's crust in the form of oxides.Atkins, P.; Jones, L.; Laverman, L. (2016).''Chemical Principles'', 7th edition. Freeman. Many major classes of organic molecules in living organisms contain oxygen atoms, such as proteins, nucleic acids, carbohydrates, and fats, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moscow State University
M. V. Lomonosov Moscow State University (MSU; russian: Московский государственный университет имени М. В. Ломоносова) is a public research university in Moscow, Russia and the most prestigious university in the country. The university includes 15 research institutes, 43 faculties, more than 300 departments, and six branches (including five foreign ones in the Commonwealth of Independent States countries). Alumni of the university include past leaders of the Soviet Union and other governments. As of 2019, 13 List of Nobel laureates, Nobel laureates, six Fields Medal winners, and one Turing Award winner had been affiliated with the university. The university was ranked 18th by ''The Three University Missions Ranking'' in 2022, and 76th by the ''QS World University Rankings'' in 2022, #293 in the world by the global ''Times Higher World University Rankings'', and #326 by ''U.S. News & World Report'' in 2022. It was the highest-ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bengt Aurivillius
Bengt Aurivillius (4 December, 1918 in Linköping – 2 May, 1994 in St. Peter's Parish, Malmöhus County) was a Swedish chemist known for his research in metal and mixed oxides. Education and career Aurivillius received his basic scientific education at the then Stockholm University where he graduated in 1937 and earned a fil. lic. in 1943."Trio of professors appointed 'Monday's Council'", ''Svenska Dagbladet'' 1965-07-27, s.2 By 1949, he had made some important discoveries about the oxidation of mixed metals, which became quite prominent in the world of chemistry. He completed his dissertation, "X-ray Examinations of Bismuth Oxifluoride and Mixed Oxides with Trivalent Bismuth", at Stockholm University in 1951. Aurivillius joined the Swedish National Defence Research Institute in 1952, where he worked first as a research engineer and later senior researcher. By 1960, Aurivillius was a docent of physical chemistry and acting senior lecturer at the Stockholm University. In 1965, he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferroelectricity
Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoelectric and pyroelectric, with the additional property that their natural electrical polarization is reversible. The term is used in analogy to ferromagnetism, in which a material exhibits a permanent magnetic moment. Ferromagnetism was already known when ferroelectricity was discovered in 1920 in Rochelle salt by Joseph Valasek.See and Thus, the prefix ''ferro'', meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not contain iron. Materials that are both ferroelectric ''and'' ferromagnetic are known as multiferroics. Polarization When most materials are electrically polarized, the polarization induced, ''P'', is almost exactly proportional to the applied external electric field ''E''; so the polarization is a linear fun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Co-fired Ceramic
Co-fired ceramic devices are monolithic, ceramic microelectronic devices where the entire ceramic support structure and any conductive, resistive, and dielectric materials are fired in a kiln at the same time. Typical devices include capacitors, inductors, resistors, transformers, and hybrid circuits. The technology is also used for robust assembly and packaging of electronic components multi-layer packaging in the electronics industry, such as military electronics, MEMS, microprocessor and RF applications. Co-fired ceramic devices are fabricated using a multilayer approach. The starting material is composite green tapes, consisting of ceramic particles mixed with polymer binders. The tapes are flexible and can be machined, for example, using cutting, milling, punching and embossing. Metal structures can be added to the layers, commonly using filling and screen printing. Individual tapes are then bonded together in a lamination procedure before the devices are fired in a kiln, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ruddlesden-Popper Phase
Ruddlesden-Popper (RP) phases are a type of perovskite structure that consists of two-dimensional perovskite-like slabs interleaved with cations. The general formula of an RP phase is ''An+1BnX3n+1'', where ''A'' and ''B'' are cations, ''X'' is an anion (e.g., oxygen), and ''n'' is the number of octahedral layers in the perovskite-like stack. Generally, it has a phase structure that results from the intergrowth of perovskite-type and NaCl-type (i.e., rocksalt-type) structures. These phases are named after S.N. Ruddlesden and P. Popper, who first synthesized and described a Ruddlesden-Popper structure in 1957. Crystal structure The general RP formula ''An+1BnX3n+1'' can be written ''An-1A’2BnX3n+1'', where ''A'' and ''A’'' are alkali, alkaline earth, or rare earth metals and ''B'' is a transition metal. The ''A'' cations are located in the perovskite layer and are 12-fold cuboctahedral coordinated by the anions (CN = 12). The ''A’'' cations have a coordination number of 9 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bismuth Compounds
Bismuth compounds are compounds containing the element bismuth (Bi). Bismuth forms trivalent and pentavalent compounds, the trivalent ones being more common. Many of its chemical properties are similar to those of arsenic and antimony, although they are less toxic than derivatives of those lighter elements. Oxides and sulfides At elevated temperatures, the vapors of the metal combine rapidly with oxygen, forming the yellow trioxide, . Wiberg, p. 768. Greenwood, p. 553. When molten, at temperatures above 710 °C, this oxide corrodes any metal oxide and even platinum. Krüger, p. 185 On reaction with a base, it forms two series of oxyanions: , which is polymeric and forms linear chains, and . The anion in is a cubic octameric anion, , whereas the anion in is tetrameric. The dark red bismuth(V) oxide, , is unstable, liberating gas upon heating. The compound NaBiO3 is a strong oxidising agent. Greenwood, p. 578. Bismuth sulfide, , occurs naturally in bismuth ores. It i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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