Strontium titanate

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Strontium titanate
Tausonite.jpg
Names
Systematic IUPAC name
Strontium(2+) oxotitaniumbis(olate)[ citation needed ]
Other names
Strontium titanium oxide
Tausonite
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.846
EC Number 235-044-1
MeSH Strontium+titanium+oxide
PubChem CID
Properties
SrTiO
3
Molar mass 183.49 g/mol
AppearanceWhite, opaque crystals
Density 5.11 g/cm3
Melting point 2,080 °C (3,780 °F; 2,350 K)
insoluble
2.394
Structure
Perovskite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Strontium titanate is an oxide of strontium and titanium with the chemical formula Sr Ti O 3. At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure. At low temperatures it approaches a ferroelectric phase transition with a very large dielectric constant ~104 but remains paraelectric down to the lowest temperatures measured as a result of quantum fluctuations, making it a quantum paraelectric. [1] It was long thought to be a wholly artificial material, until 1982 when its natural counterpart—discovered in Siberia and named tausonite—was recognised by the IMA. Tausonite remains an extremely rare mineral in nature, occurring as very tiny crystals. Its most important application has been in its synthesized form wherein it is occasionally encountered as a diamond simulant, in precision optics, in varistors, and in advanced ceramics.

Oxide chemical compound with at least one oxygen atom

An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– atom. Metal oxides thus typically contain an anion of oxygen in the oxidation state of −2. Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water. Hydrocarbon combustion affords the two principal carbon oxides: carbon monoxide and carbon dioxide. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion. Individual elements can often form multiple oxides, each containing different amounts of the element and oxygen. In some cases these are distinguished by specifying the number of atoms as in carbon monoxide and carbon dioxide, and in other cases by specifying the element's oxidation number, as in iron(II) oxide and iron(III) oxide. Certain elements can form many different oxides, such as those of nitrogen.

Strontium Chemical element with atomic number 38

Strontium is the chemical element with symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to air. Strontium has physical and chemical properties similar to those of its two vertical neighbors in the periodic table, calcium and barium. It occurs naturally mainly in the minerals celestine and strontianite, and is mostly mined from these. While natural strontium is stable, the synthetic 90Sr isotope is radioactive and is one of the most dangerous components of nuclear fallout, as strontium is absorbed by the body in a similar manner to calcium. Natural stable strontium, on the other hand, is not hazardous to health.

Titanium Chemical element with atomic number 22

Titanium is a chemical element with symbol Ti and atomic number 22. It is a lustrous transition metal with a silver color, low density, and high strength. Titanium is resistant to corrosion in sea water, aqua regia, and chlorine.

Contents

The name tausonite was given in honour of Lev Vladimirovich Tauson (1917–1989), a Russian geochemist. Disused trade names for the synthetic product include strontium mesotitanate, Fabulite, [2] Diagem, and Marvelite. Other than its type locality of the Murun Massif in the Sakha Republic, natural tausonite is also found in Cerro Sarambi, Concepción department, Paraguay; and along the Kotaki River of Honshū, Japan. [3] [4]

Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the entire Solar System, and has made important contributions to the understanding of a number of processes including mantle convection, the formation of planets and the origins of granite and basalt.

Sakha Republic First-level administrative division of Russia

The Republic of Sakha (Yakutia) (Russian: Республика Саха, tr.Respublika Sakha , IPA: [rʲɪsˈpublʲɪkə sɐˈxa jɪˈkutʲɪjə]; Yakut: Саха Өрөспүүбүлүкэтэ, translit. Sakha Öröspüübülükete, IPA: [saˈxa øɾøsˈpyːbylykete] is a federal Russian republic. It had a population of 958,528 at the 2010 Census, mainly ethnic Yakuts and Russians.

Paraguay republic in South America

Paraguay, officially the Republic of Paraguay, is a country of South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Although it is one of the only two landlocked countries in South America, the country has coasts, beaches and ports on the Paraguay and Paraná rivers that give exit to the Atlantic Ocean through the Paraná-Paraguay Waterway. Due to its central location in South America, it is sometimes referred to as Corazón de Sudamérica.

Properties

Atomic resolution image of SrTiO3. Brighter atoms are Sr and darker ones are Ti Stohrem.jpg
Atomic resolution image of SrTiO3. Brighter atoms are Sr and darker ones are Ti
Structure of SrTiO3. The red spheres are oxygens, blue are Ti cations, and the green ones are Sr . Perovskite.jpg
Structure of SrTiO3. The red spheres are oxygens, blue are Ti cations, and the green ones are Sr .

SrTiO3 has an indirect band gap of 3.25 eV and a direct gap of 3.75 eV [5] in the typical range of semiconductors. Synthetic strontium titanate has a very large dielectric constant (300) at room temperature and low electric field. It has a specific resistivity of over 109 Ω-cm for very pure crystals. [6] It is also used in high-voltage capacitors. Introducing mobile charge carriers by doping leads to Fermi-liquid metallic behavior already at very low charge carrier densities. [7] At high electron densities strontium titanate becomes superconducting below 0.35 K and was the first insulator and oxide discovered to be superconductive. [8]

Band gap energy range in a solid where no electron states can exist; energy difference (in electron volts) between the top of the valence band and the bottom of the conduction band in insulators and semiconductors

In solid-state physics, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote a valence electron bound to an atom to become a conduction electron, which is free to move within the crystal lattice and serve as a charge carrier to conduct electric current. It is closely related to the HOMO/LUMO gap in chemistry. If the valence band is completely full and the conduction band is completely empty, then electrons cannot move in the solid; however, if some electrons transfer from the valence to the conduction band, then current can flow. Therefore, the band gap is a major factor determining the electrical conductivity of a solid. Substances with large band gaps are generally insulators, those with smaller band gaps are semiconductors, while conductors either have very small band gaps or none, because the valence and conduction bands overlap.

A semiconductor material has an electrical conductivity value falling between that of a metal, like copper, gold, etc. and an insulator, such as glass. Their resistance decreases as their temperature increases, which is behaviour opposite to that of a metal. Their conducting properties may be altered in useful ways by the deliberate, controlled introduction of impurities ("doping") into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Some examples of semiconductors are silicon, germanium, and gallium arsenide. After silicon, gallium arsenide is the second most common semiconductor used in laser diodes, solar cells, microwave frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.

Superconductivity physical phenomenon

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials, called superconductors, when cooled below a characteristic critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 8, 1911, in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.

Strontium titanate is both much denser (specific gravity 4.88 for natural, 5.13 for synthetic) and much softer (Mohs hardness 5.5 for synthetic, 6-6.5 for natural) than diamond. Its crystal system is cubic and its refractive index (2.410—as measured by sodium light, 589.3 nm) is nearly identical to that of diamond (at 2.417), but the dispersion (the optical property responsible for the "fire" of the cut gemstones) of strontium titanate is 4.3x that of diamond, at 0.190 (B–G interval). This results in a shocking display of fire compared to diamond and diamond simulants such as YAG, GAG, GGG, Cubic Zirconia, and Moissanite. [3] [4]

Specific gravity Relative density compared to water

Specific gravity is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance for liquids is nearly always water at its densest ; for gases it is air at room temperature. Nonetheless, the temperature and pressure must be specified for both the sample and the reference. Pressure is nearly always 1 atm (101.325 kPa).

Mohs scale of mineral hardness qualitative ordinal scale characterizing scratch resistance of various minerals

The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, some of which are more quantitative. The method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c. 77 AD. While greatly facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting.

Diamond Allotrope of carbon often used as a gemstone

Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form, but diamond almost never converts to it. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are utilized in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.

Synthetics are usually transparent and colourless, but can be doped with certain rare earth or transition metals to give reds, yellows, browns, and blues. Natural tausonite is usually translucent to opaque, in shades of reddish brown, dark red, or grey. Both have an adamantine (diamond-like) lustre. Strontium titanate is considered extremely brittle with a conchoidal fracture; natural material is cubic or octahedral in habit and streaks brown. Through a hand-held (direct vision) spectroscope, doped synthetics will exhibit a rich absorption spectrum typical of doped stones. Synthetic material has a melting point of ca. 2080 °C (3776 °F) and is readily attacked by hydrofluoric acid. [3] [4] Under extremely low oxygen partial pressure, strontium titanate decomposes via incongruent sublimation of strontium well below the melting temperature. [9]

A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance to alter the electrical or optical properties of the substance. In the case of crystalline substances, the atoms of the dopant very commonly take the place of elements that were in the crystal lattice of the base material. The crystalline materials are frequently either crystals of a semiconductor such as silicon and germanium for use in solid-state electronics, or transparent crystals for use in the production of various laser types; however, in some cases of the latter, noncrystalline substances such as glass can also be doped with impurities.

In chemistry, the term transition metal has three possible meanings:

Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux, meaning "light", and generally implies radiance, gloss, or brilliance.

At temperatures lower than 105 K, its cubic structure transforms to tetragonal. [10] Its monocrystals can be used as optical windows and high-quality sputter deposition targets.

Sputter deposition physical vapor deposition (PVD) method of thin film deposition by sputtering

Sputter deposition is a physical vapor deposition (PVD) method of thin film deposition by sputtering. This involves ejecting material from a "target" that is a source onto a "substrate" such as a silicon wafer. Resputtering is re-emission of the deposited material during the deposition process by ion or atom bombardment. Sputtered atoms ejected from the target have a wide energy distribution, typically up to tens of eV. The sputtered ions can ballistically fly from the target in straight lines and impact energetically on the substrates or vacuum chamber. Alternatively, at higher gas pressures, the ions collide with the gas atoms that act as a moderator and move diffusively, reaching the substrates or vacuum chamber wall and condensing after undergoing a random walk. The entire range from high-energy ballistic impact to low-energy thermalized motion is accessible by changing the background gas pressure. The sputtering gas is often an inert gas such as argon. For efficient momentum transfer, the atomic weight of the sputtering gas should be close to the atomic weight of the target, so for sputtering light elements neon is preferable, while for heavy elements krypton or xenon are used. Reactive gases can also be used to sputter compounds. The compound can be formed on the target surface, in-flight or on the substrate depending on the process parameters. The availability of many parameters that control sputter deposition make it a complex process, but also allow experts a large degree of control over the growth and microstructure of the film.

Strontium titanate single crystal substrates (5x5x0.5mm). The transparent substrate (left) is pure SrTiO3 and the black substrate is doped with 0.5% (weight) of niobium SrTiO3 single crystal substrates.png
Strontium titanate single crystal substrates (5x5x0.5mm). The transparent substrate (left) is pure SrTiO3 and the black substrate is doped with 0.5% (weight) of niobium

SrTiO3 is an excellent substrate for epitaxial growth of high-temperature superconductors and many oxide-based thin films. It is particularly well known as the substrate for the growth of the lanthanum aluminate-strontium titanate interface. Doping strontium titanate with niobium makes it electrically conductive, being one of the only conductive commercially available single crystal substrates for the growth of perovskite oxides. Its bulk lattice parameter of 3.905Å makes it suitable as the substrate for the growth of many other oxides, including the rare-earth manganites, titanates, lanthanum aluminate (LaAlO3), strontium ruthenate (SrRuO3) and many others. Oxygen vacancies are fairly common in SrTiO3 crystals and thin films. Oxygen vacancies induce free electrons in the conduction band of the material, making it more conductive and opaque. These vacancies can be caused by exposure to reducing conditions, such as high vacuum at elevated temperatures.

High-quality, epitaxial SrTiO3 layers can also be grown on silicon without forming silicon dioxide, thereby making SrTiO3 an alternative gate dielectric material. This also enables the integration of other thin film perovskite oxides onto silicon. [11]

SrTiO3 has been shown to possess persistent photoconductivity where exposing the crystal to light will increase its electrical conductivity by over 2 orders of magnitude. After the light is turned off, the enhanced conductivity persists for several days, with negligible decay. [12] [13]

Due to the significant ionic and electronic conduction of SrTiO3, it is potent to be used as the mixed conductor. [14]

Synthesis

A plate cut out of synthetic SrTiO3 crystal Stocrystal.jpg
A plate cut out of synthetic SrTiO3 crystal

Synthetic strontium titanate was one of several titanates patented during the late 1940s and early 1950s; other titanates included barium titanate and calcium titanate. Research was conducted primarily at the National Lead Company (later renamed NL Industries) in the United States, by Leon Merker and Langtry E. Lynd. Merker and Lynd first patented the growth process on February 10, 1953; a number of refinements were subsequently patented over the next four years, such as modifications to the feed powder and additions of colouring dopants.

A modification to the basic Verneuil process (also known as flame-fusion) is the favoured method of growth. An inverted oxy-hydrogen blowpipe is used, with feed powder mixed with oxygen carefully fed through the blowpipe in the typical fashion, but with the addition of a third pipe to deliver oxygen—creating a tricone burner. The extra oxygen is required for successful formation of strontium titanate, which would otherwise fail to oxidize completely due to the titanium component. The ratio is ca. 1.5 volumes of hydrogen for each volume of oxygen. The highly purified feed powder is derived by first producing titanyl double oxalate salt (SrTiO(C 2O4)2·2H2O) by reacting strontium chloride (SrCl 2) and oxalic acid ((COOH)2.2H2O) with titanium tetrachloride (TiCl4). The salt is washed to completely eliminate chloride, heated to 1000 °C in order to produce a free-flowing granular powder of the required composition, and is then ground and sieved to ensure all particles are between 0.2–0.5 micrometres in size. [15]

The feed powder falls through the oxyhydrogen flame, melts, and lands on a rotating and slowly descending pedestal below. The height of the pedestal is constantly adjusted to keep its top at the optimal position below the flame, and over a number of hours the molten powder cools and crystallises to form a single pedunculated pear or boule crystal. This boule is usually no larger than 2.5 centimetres in diameter and 10 centimetres long; it is an opaque black to begin with, requiring further annealing in an oxidizing atmosphere in order to make the crystal colourless and to relieve strain. This is done at over 1000 °C for 12 hours. [15]

Thin films of SrTiO3 can be grown epitaxially by various methods, including pulsed laser deposition, molecular beam epitaxy, RF sputtering and atomic layer deposition. As in most thin films, different growth methods can result in significantly different defect and impurity densities and crystalline quality, resulting in a large variation of the electronic and optical properties.

Use as a diamond simulant

Its cubic structure and high dispersion once made synthetic strontium titanate a prime candidate for simulating diamond. Beginning ca. 1955, large quantities of strontium titanate were manufactured for this sole purpose. Strontium titanate was in competition with synthetic rutile ("titania") at the time, and had the advantage of lacking the unfortunate yellow tinge and strong birefringence inherent to the latter material. While it was softer, it was significantly closer to diamond in likeness. Eventually, however, both would fall into disuse, being eclipsed by the creation of "better" simulants: first by yttrium aluminium garnet (YAG) and followed shortly after by gadolinium gallium garnet (GGG); and finally by the (to date) ultimate simulant in terms of diamond-likeness and cost-effectiveness, cubic zirconia. [16]

Despite being outmoded, strontium titanate is still manufactured and periodically encountered in jewellery. It is one of the most costly of diamond simulants, and due to its rarity collectors may pay a premium for large i.e. >2 carat (400 mg) specimens. As a diamond simulant, strontium titanate is most deceptive when mingled with melée i.e. <0.20 carat (40 mg) stones and when it is used as the base material for a composite or doublet stone (with, e.g., synthetic corundum as the crown or top of the stone). Under the microscope, gemmologists distinguish strontium titanate from diamond by the former's softness—manifested by surface abrasions—and excess dispersion (to the trained eye), and occasional gas bubbles which are remnants of synthesis. Doublets can be detected by a join line at the girdle ("waist" of the stone) and flattened air bubbles or glue visible within the stone at the point of bonding. [17] [18] [19]

Use in radioisotope thermoelectric generators

Due to its high melting point and insolubility, strontium titanate has been used as a strontium-90-containing material in radioisotope thermoelectric generators, such as the US Sentinel and Soviet Beta-M series. [20] [21]

Use in solid oxide fuel cells

Strontium titanate’s mixed conductivity it has attracted attention for use in solid oxide fuel cells (SOFCs). It is a good fit because, as described above, it demonstrates both electronic and ionic conductivity which is useful for SOFC electrodes because on both sides of the cell there is an exchange of gas, oxygen ion in the material and electrons.

(anode)

(cathode)

Strontium titanate is doped with different materials for use on different sides of a fuel cell. On the fuel side (anode), where the first reaction occurs, it is often doped with lanthanum to form lanthanum-doped strontium titanate (LST). In this case, the A-site, or position in the unit cell where strontium usually sits, is sometimes filled by lanthanum instead, this causes the material to exhibit n-type semiconductor properties, including electronic conductivity. It also shows oxygen ion conduction due to the perovskite structure tolerance for oxygen vacancies. This material has a thermal coefficient of expansion similar to that of the common electrolyte yttria-stabilized zirconia (YSZ), chemical stability during the reactions which occur at fuel cell electrodes, and electronic conductivity of up to 360 S/cm under SOFC operating conditions. [22] Another key advantage of these LST is that it shows a resistance to sulfur poisoning, which is an issue with the currently used nickel - ceramic (cermet) anodes. [23]

Another related compound is strontium titanium ferrite (STF) which is used a cathode (oxygen-side) material in SOFCs. This material also shows mixed ionic and electronic conductivity which is important as it means the reduction reaction which happens at the cathode can occur over a wider area. [24] Building on this material by adding cobalt on the B-site (replacing titanium) as well as iron, we have the material STFC, or cobalt-substituted STF, which shows remarkable stability as a cathode material as well as lower polarization resistance than other common cathode materials such as lanthanum strontium cobalt ferrite. These cathodes also have the advantage of not containing rare earth metals which make them cheaper than many of the alternatives. [25]

Related Research Articles

Dielectric electrically poorly conducting or non-conducting, non-metallic substance of which charge carriers are generally not free to move

A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor but only slightly shift from their average equilibrium positions causing dielectric polarization. Because of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the opposite direction. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axes align to the field.

Zirconium dioxide chemical compound

Zirconium dioxide, sometimes known as zirconia, is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synthesized in various colours for use as a gemstone and a diamond simulant.

Perovskite (structure)

A perovskite is any material with the same type of crystal structure as calcium titanium oxide (CaTiO3), known as the perovskite structure, or XIIA2+VIB4+X2−3 with the oxygen in the edge centers. Perovskites take their name from the mineral, which was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist L. A. Perovski (1792–1856). The general chemical formula for perovskite compounds is ABX3, where 'A' and 'B' are two cations of very different sizes, and X is an anion that bonds to both. The 'A' atoms are larger than the 'B' atoms. The ideal cubic structure has the B cation in 6-fold coordination, surrounded by an octahedron of anions, and the A cation in 12-fold cuboctahedral coordination. The relative ion size requirements for stability of the cubic structure are quite stringent, so slight buckling and distortion can produce several lower-symmetry distorted versions, in which the coordination numbers of A cations, B cations or both are reduced.

A regenerative fuel cell or reverse fuel cell (RFC) is a fuel cell run in reverse mode, which consumes electricity and chemical B to produce chemical A. By definition, the process of any fuel cell could be reversed. However, a given device is usually optimized for operating in one mode and may not be built in such a way that it can be operated backwards. Standard fuel cells operated backwards generally do not make very efficient systems unless they are purpose-built to do so as with high-pressure electrolysers, regenerative fuel cells, solid-oxide electrolyser cells and unitized regenerative fuel cells.

Solid oxide fuel cell fuel cell that has a ceramic electrolyte

A solid oxide fuel cell is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte.

Lead zirconate titanate intermetallic inorganic chemical compound

Lead zirconate titanate is an inorganic compound with the chemical formula Pb[ZrxTi1-x]O3 (0≤x≤1). Also called PZT, it is a ceramic perovskite material that shows a marked piezoelectric effect, meaning that the compound changes shape when an electric field is applied. It is used in a number of practical applications such as ultrasonic transducers and piezoelectric resonators. It is a white to off-white solid.

Diamond simulant

A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond. Simulants are distinct from synthetic diamonds, which are actual diamonds having the same material properties as natural diamonds. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection.

Barium titanate chemical compound

Barium titanate is an inorganic compound with chemical formula BaTiO3. Barium titanate appears white as a powder and is transparent when prepared as large crystals. It is a ferroelectric ceramic material that exhibits the photorefractive effect and piezoelectric properties. It is used in capacitors, electromechanical transducers and nonlinear optics.

In materials science, fast ion conductors are solids with highly mobile ions. These materials are important in the area of solid-state ionics, and are also known as solid electrolytes and superionic conductors. These materials are useful in batteries and various sensors. Fast ion conductors are used primarily in solid oxide fuel cells. As solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid crystal structure.

Lanthanum strontium cobalt ferrite (LSCF), also called lanthanum strontium cobaltite ferrite is a specific ceramic oxide derived from lanthanum cobaltite of the ferrite group. It is a phase containing lanthanum(III) oxide, strontium oxide, cobalt oxide and iron oxide.

Lanthanum strontium manganite

Lanthanum strontium manganite (LSM or LSMO) is an oxide ceramic material with the general formula La1−xSrxMnO3, where x describes the doping level.

The Burns temperature, Td, is the temperature where a ferroelectric material, previously in paraelectric state, starts to present randomly polarized nanoregions, that are polar precursor cluster. This behaviour is typical of several, but not all, ferroelectric materials, and was observed in lead titanate (PbTiO3), potassium niobate (KNbO3), lead lanthanum zirconate titanate (PLZT), lead magnesium niobate (PMN), lead zinc niobate (PZN), K2Sr4(NbO3)10, and strontium barium niobate (SBN), Na1/2Bi1/2O3(NBT).

Solid oxide electrolyser cell

A solid oxide electrolyzer cell (SOEC) is a solid oxide fuel cell that runs in regenerative mode to achieve the electrolysis of water by using a solid oxide, or ceramic, electrolyte to produce hydrogen gas and oxygen. The production of pure hydrogen is compelling because it is a clean fuel that can be stored easily, thus making it a potential alternative to batteries, which have a low storage capacity and create high amounts of waste materials. Electrolysis is currently the most promising method of hydrogen production from water due to high efficiency of conversion and relatively low required energy input when compared to thermochemical and photocatalytic methods.

Quantum paraelectricity

Quantum paraelectricity is a type of incipient ferroelectricity where the onset of ferroelectric order is suppressed by quantum fluctuations. From the soft mode theory of ferroelectricity, this occurs when a ferroelectric instability is stabilized by quantum fluctuations. In this case the soft-mode frequency never becomes unstable as opposed to a regular ferroelectric.

Gadolinium-doped ceria (GDC) (known alternatively as gadolinia-doped ceria, gadolinium-doped cerium oxide, cerium(IV) oxide, gadolinium-doped, and GCO, formula Gd:CeO2) is a ceramic electrolyte used in solid oxide fuel cells (SOFCs). It has a cubic structure and a density of around 7.2 g/cm3 in its oxidised form. It is one of a class of ceria-doped electrolytes with higher ionic conductivity and lower operating temperatures (<700 °C) than those of yttria-stabilized zirconia, the material most commonly used in SOFCs. Because YSZ requires operating temperatures of 800–1000 °C to achieve maximal ionic conductivity, the associated energy and costs make GDC a more optimal (even "irreplaceable", according to researchers from the Fraunhofer Institute) material for commercially viable SOFCs.

Lanthanum manganite is an inorganic compound with the formula LaMnO3, often abbreviated as LMO. Lanthanum manganite is formed in the perovskite structure, consisting of oxygen octahedra with a central Mn atom. The cubic perovskite structure is distorted into an orthorhombic structure by a strong Jahn–Teller distortion of the oxygen octahedra.

LSAT is the most common name for the inorganic compound lanthanum aluminate - strontium aluminium tantalate, which has the chemical formula (LaAlO3)0.3(Sr2TaAlO6)0.7 or its less common alternative: (La0.18Sr0.82)(Al0.59Ta0.41)O3. LSAT is a hard, optically transparent ceramic oxide of the elements lanthanum, aluminum, strontium and tantalum. LSAT has the perovskite crystal structure, and its most common use is as a single crystal substrate for the growth of epitaxial thin films.

Lanthanum aluminate is an inorganic compound with the formula LaAlO3, often abbreviated as LAO. It is an optically transparent ceramic oxide with a distorted perovskite structure.

A complex oxide is a chemical compound that contains oxygen and at least two other elements. Complex oxide materials are notable for their wide range of magnetic and electronic properties, such as ferromagnetism, ferroelectricity, and high-temperature superconductivity. These properties often come from their strongly correlated electrons in d or f orbitals.

Mixed conductor Mixed ion-electron conductor

Mixed conductor which is known as mixed ion-electron conductor(MIEC) refers to a single-phase material which has a significant conduction ionically and electronically. Due to the mixed conduction, a formally neutral species can transport in a solid and therefore mass storage and redistribution are enabled. Mixed conductors are well known in conjugation with high-temperature superconductivity and are able to capacitate rapid solid-state reactions.

References

  1. K. A. Muller & H. Burkard (1979). "SrTiO3: An intrinsic quantum paraelectric below 4 K". Phys. Rev. B. 19 (7): 3593–3602. Bibcode:1979PhRvB..19.3593M. doi:10.1103/PhysRevB.19.3593.
  2. Mottana, Annibale (March 1986). "Una brillante sintesi". Scienza e Dossier (in Italian). Giunti. 1 (1): 9.
  3. 1 2 3 "Tausonite". Webmineral. Retrieved 2009-06-06.
  4. 1 2 3 "Tausonite". Mindat. Retrieved 2009-06-06.
  5. K. van Benthem, C. Elsässer and R. H. French (2001). "Bulk electronic structure of SrTiO3: Experiment and theory". Journal of Applied Physics . 90: 6156. Bibcode:2001JAP....90.6156V. doi:10.1063/1.1415766.
  6. "http://www.espimetals.com/index.php/technical-data/248-strontium-titanate", This link is broken, new reference needed
  7. Xiao Lin, Benoît Fauqué, Kamran Behnia (2015). "Scalable T2 resistivity in a small single-component Fermi surface". Science . 349: 945. arXiv: 1508.07812 . Bibcode:2015Sci...349..945L. doi:10.1126/science.aaa8655.CS1 maint: Multiple names: authors list (link)
  8. Koonce, C. S.; Cohen, Marvin L. (1967). "Superconducting Transition Temperatures of Semiconducting SrTiO3". Phys. Rev. 163 (2): 380. Bibcode:1967PhRv..163..380K. doi:10.1103/PhysRev.163.380.
  9. C. Rodenbücher; P. Meuffels; W. Speier; M. Ermrich; D. Wrana; F. Krok; K. Szot (2017). "Stability and Decomposition of Perovskite-Type Titanates upon High-Temperature Reduction". Phys. Status Solidi RRL. 11 (9): 1700222. doi:10.1002/pssr.201700222.
  10. L. Rimai & G. A. deMars (1962). "Electron Paramagnetic Resonance of Trivalent Gadolinium Ions in Strontium and Barium Titanates". Phys. Rev. 127 (3): 702. Bibcode:1962PhRv..127..702R. doi:10.1103/PhysRev.127.702.
  11. R. A. McKee; F. J. Walker & M. F. Chisholm (1998). "Crystalline Oxides on Silicon: The First Five Monolayers" (PDF). Phys. Rev. Lett. 81 (14): 3014. Bibcode:1998PhRvL..81.3014M. doi:10.1103/PhysRevLett.81.3014.
  12. "Persistent Photoconductivity in Strontium Titanate". Department of Physics and Astronomy, Washington State University, Pullman, Washington. Retrieved 2013-11-18.
  13. "Light Exposure Increases Crystal's Electrical Conductivity 400-fold [VIDEO]". Nature World News. Retrieved 2013-11-18.
  14. "Mixed conductors". Max Planck institute for solid state research. Retrieved 16 September 2016.
  15. 1 2 H. J. Scheel & P. Capper (2008). Crystal growth technology: from fundamentals and simulation to large-scale production. Wiley-VCH. p. 431. ISBN   3-527-31762-7.
  16. R. W. Hesse (2007). Jewelrymaking through history: an encyclopedia. Greenwood Publishing Group. p. 73. ISBN   0-313-33507-9.
  17. Nassau, K. (1980). Gems made by man. Santa Monica, California: Gemological Institute of America. pp. 214–221. ISBN   0-87311-016-1.
  18. O'Donoghue, M. (2002). Synthetic, imitation & treated gemstones. Great Britain: Elsevier Butterworth-Heinemann. pp. 34, 65. ISBN   0-7506-3173-2.
  19. Read, P. G. (1999). Gemmology, second edition. Great Britain: Butterworth-Heinemann. pp. 173, 176, 177, 293. ISBN   0-7506-4411-7.
  20. "Power Sources for Remote Arctic Applications" (PDF). Washington, DC: U.S. Congress, Office of Technology Assessment. June 1994. OTA-BP-ETI-129.
  21. Standring, WJF; Selnæs, ØG; Sneve, M; Finne, IE; Hosseini, A; Amundsen, I; Strand, P (2005), Assessment of environmental, health and safety consequences of decommissioning radioisotope thermal generators (RTGs) in Northwest Russia (PDF) (StrålevernRapport 2005:4), Østerås: Norwegian Radiation Protection Authority
  22. Marina, O (2002). "Thermal, electrical, and electrocatalytical properties of lanthanum-doped strontium titanate". Solid State Ionics. 149 (1–2): 21–28. doi:10.1016/S0167-2738(02)00140-6.
  23. Gong, Mingyang; Liu, Xingbo; Trembly, Jason; Johnson, Christopher (2007). "Sulfur-tolerant anode materials for solid oxide fuel cell application". Journal of Power Sources. 168 (2): 289–298. doi:10.1016/j.jpowsour.2007.03.026.
  24. Jung, WooChul; Tuller, Harry L. (2009). "Impedance study of SrTi1−xFexO3−δ (x=0.05 to 0.80) mixed ionic-electronic conducting model cathode". Solid State Ionics. 180 (11–13): 843–847. doi:10.1016/j.ssi.2009.02.008.
  25. Zhang, Shan-Lin; Wang, Hongqian; Lu, Matthew Y.; Zhang, Ai-Ping; Mogni, Liliana V.; Liu, Qinyuan; Li, Cheng-Xin; Li, Chang-Jiu; Barnett, Scott A. (2018). "Cobalt-substituted SrTi 0.3 Fe 0.7 O 3−δ : a stable high-performance oxygen electrode material for intermediate-temperature solid oxide electrochemical cells". Energy & Environmental Science. 11 (7): 1870–1879. doi:10.1039/C8EE00449H.