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Oxonickelates
Nickel forms a series of mixed oxide compounds which are commonly called nickelates. A nickelate is an anion containing nickel or a salt containing a nickelate anion, or a double compound containing nickel bound to oxygen and other elements. Nickel can be in different or even mixed oxidation states, ranging from +1, +2, +3 to +4. The anions can contain a single nickel ion, or multiple to form a cluster ion. The solid mixed oxide compounds are often ceramics, but can also be metallic. They have a variety of electrical and magnetic properties. Rare-earth elements form a range of perovskite nickelates, in which the properties vary systematically as the rare-earth element changes. Fine tuning of properties is achievable with mixtures of elements, applying stress or pressure, or varying the physical form. Inorganic chemists call many compounds that contain nickel centred anions "nickelates". These include the chloronickelates, fluoronickelates, tetrabromonickelates, tetraiodonickelat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neodymium Nickelate
Neodymium nickelate is a nickelate of neodymium with a chemical formula NdNiO3. In this compound, the neodymium atom is in the +3 oxidation state. Preparation Neodymium nickelate can be prepared by dissolving neodymium(III) oxide and nickel(II) oxide in nitric acid, followed by heating the mixture in an oxygen atmosphere. It can also be prepared by pyrolyzing a mixture of nickel nitrate and neodymium nitrate. It decomposes in high temperature (950 °C) by nitrogen: :4 NdNiO3 → 2 Nd2NiO4 + 2 NiO + O2 It can also be reduced to the monovalent nickel compound NdNiO2 by sodium hydride at 160 °C. Physical properties Neodymium nickelate shows metal-insulator transition (MIT) under low temperature. The temperature at which it transforms (TMIT) is 200K, which is higher than praseodymium nickelate (130K) but lower than samarium nickelate (400K). It transforms from antiferromagnetism to paramagnetism. It has demonstrated to be a first-order phase transition (this applies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rare-earth Element
The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silvery-white soft heavy metals. Compounds containing rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes. Scandium and yttrium are considered rare-earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties, but have different electronic and magnetic properties. These metals tarnish slowly in air at room temperature and react slowly with cold water to form hydroxides, liberating hydrogen. They react with steam to form oxides, and at elevated temperature (400°C) ignite spontaneously. These elements and their compounds have no biological function other than in several specialized enzymes, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuel Cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. The first fuel cells were invented by Sir William Grove in 1838. The first commercial use of fuel cells came more than a century later following the invention of the hydrogen–oxygen fuel cell by Francis Thomas Bacon in 1932. The alkaline fuel cell, also known as the Bacon fuel cell after its inventor, has been used in NASA space programs since the mid-1960s to generate power for satellites and space capsules. Since then, fuel cells have b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nickel Compounds
Nickel compounds are chemical compounds containing the element nickel which is a member of the group 10 of the periodic table. Most compounds in the group have an oxidation state of +2. Nickel is classified as a transition metal with nickel(II) having much chemical behaviour in common with iron(II) and cobalt(II). Many salts of nickel(II) are isomorphous with salts of magnesium due to the ionic radii of the cations being almost the same. Nickel forms many coordination complexes. Nickel tetracarbonyl was the first pure metal carbonyl produced, and is unusual in its volatility. Metalloproteins containing nickel are found in biological systems. Nickel forms simple binary compounds with non metals including halogens, chalcogenides, and pnictides. Nickel ions can act as a cation in salts with many acids, including common oxoacids. Salts of the hexaaqua ion (Ni2+) are especially well known. Many double salts containing nickel with another cation are known. There are organic acid salts. N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manganate
In inorganic nomenclature, a manganate is any negatively charged molecular entity with manganese as the central atom.. However, the name is usually used to refer to the tetraoxidomanganate(2−) anion, MnO, also known as manganate(VI) because it contains manganese in the +6 oxidation state. Manganates are the only known manganese(VI) compounds.. Other manganates include hypomanganate or manganate(V), , permanganate or manganate(VII), , and the dimanganate or dimanganate(III) . A manganate(IV) anion has been prepared by radiolysis of dilute solutions of permanganate.. It is mononuclear in dilute solution, and shows a strong absorption in the ultraviolet and a weaker absorption at 650 nm. Structure The manganate(VI) ion is tetrahedral, similar to sulfate or chromate: indeed, manganates are often isostructural with sulfates and chromates, a fact first noted by Eilhard Mitscherlich in 1831.. The manganese–oxygen distance is 165.9 pm, about 3 pm longer than in p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nickel Manganese Oxides
Nickel manganese oxides, or nickel manganates, are spinel structure compounds of Nickel, Manganese and 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 wel ... of the form: Some common forms are Ni2MnO4, NiMn2O4, and Ni1.5Mn1.5O4 They are most commonly formulated for use in thin film resistors and thermistors. The resistivity and temperature coefficient can be accurately controlled in the manufacturing process. In nickel-metal hydride batteries the addition of manganese oxide provides for formation of spinel structure nickel manganates in various oxidation states, with higher conductivity and charge capacity than nickel hydroxides alone. Magnetic properties of nickel manganates. Although nickel manganates exhibit ferromagnetic behaviour at low temperatures, they have a paramagne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiferromagnetic
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. This is, like ferromagnetism and ferrimagnetism, a manifestation of ordered magnetism. The phenomenon of antiferromagnetism was first introduced by Lev Landau in 1933. Generally, antiferromagnetic order may exist at sufficiently low temperatures, but vanishes at and above the Néel temperature – named after Louis Néel, who had first identified this type of magnetic ordering. Above the Néel temperature, the material is typically paramagnetic. Measurement When no external field is applied, the antiferromagnetic structure corresponds to a vanishing total magnetization. In an external magnetic field, a kind of ferrimagnetic behavior may be displayed in the antiferromagnetic phase, with the absolute value of one of the sublattice magneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Metal
A polar metal, metallic ferroelectric, or ferroelectric metal is a metal that contains an electric dipole moment. Its components have an ordered electric dipole. Such metals should be unexpected, because the charge should conduct by way of the free electrons in the metal and neutralize the polarized charge. However they do exist. Probably the first report of a polar metal was in single crystals of the cuprate superconductors YBa2Cu3O7−δ,. A polarization was observed along one (001) axis by pyroelectric effect measurements, and the sign of the polarization was shown to be reversible, while its magnitude could be increased by poling with an electric field. The polarization was found to disappear in the superconducting state. The lattice distortions responsible were considered to be a result of oxygen ion displacements induced by doped charges that break inversion symmetry. The effect was utilized for fabrication of pyroelectric detectors for space applications, having the advantage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-temperature Superconductor
High-temperature superconductors (abbreviated high-c or HTS) are defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen. The adjective "high temperature" is only in respect to previously known superconductors, which function at even colder temperatures close to absolute zero. In absolute terms, these "high temperatures" are still far below ambient, and therefore require cooling. The first high-temperature superconductor was discovered in 1986, by IBM researchers Bednorz and Müller, who were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high-c materials are type-II superconductors. The major advantage of high-temperature superconductors is that they can be cooled by using liquid nitrogen, as opposed to the previously known superconductors which require expensive and hard-to-handle coolants, primarily liquid helium. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chloronickelate
Tetrachloronickelate is the metal complex with the formula iCl4sup>2−. Salts of the complex are available with a variety of cations, but a common one is tetraethylammonium. When concentrated lithium chloride and nickel chloride solution in water is mixed, only a pentaaquachloro complex is formed: i(H2O)5Clsup>+. However in other organic solvents, or molten salts the tetrachloronickelate ion can form. Nickel can be separated from such a solution in water or methanol, by partitioning it into a cyclohexane solution of amines. Organic ammonium salts of the type (R3NH)2 iCl4are often thermochromic (R = Me, Et, Pr). Near room temperature, these salts are yellow , but these solids become blue when heated to near 70 °C. The bright blue color is characteristic of tetrahedral iCl4sup>2−, the intensity being a consequence of the Laporte selection rule. The yellow color results from a polymer consisting of octahedral Ni centers. The corresponding tetrabromonickelates are also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cuprate
Cuprate loosely refers to a material that can be viewed as containing anionic copper complexes. Examples include tetrachloridocuprate ( uCl4sup>2−), the superconductor YBa2Cu3O7, and the organocuprates (e.g., dimethylcuprate u(CH3)2sup>−). The term cuprates derives from the Latin word for copper, ''cuprum''. The term is mainly used in three contexts: oxide materials, anionic coordination complexes, and anionic organocopper compounds. Oxides One of the simplest oxide-based cuprates is the copper(III) oxide KCuO2, also known as "potassium cuprate(III)". This species can be viewed as the K+ salt of the polyanion []''n''. As such the material is classified as a cuprate. This dark blue diamagnetic solid is produced by heating potassium peroxide and copper(II) oxide in an atmosphere of oxygen: :K2O2 + 2 CuO → 2 KCuO2 Sodium cuprate(III) NaCuO2 and potassium cuprate(III) KCuO2 can also be produced by using hypochlorites or hypobromites to oxidize copper hydroxide unde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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