LSAT (oxide)

LSAT (oxide)
Names
	Other names lanthanum aluminate - strontium aluminium tantalate
Identifiers
PubChem CID	91865216 ;
Properties
Chemical formula	(LaAlO3)0.3(Sr2TaAlO6)0.7
Density	6.74 g/cm3
Melting point	1,840 °C (3,340 °F; 2,110 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Last updated September 26, 2023

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: (La_0.18Sr_0.82)(Al_0.59Ta_0.41)O₃. LSAT is a hard, optically transparent oxide of the elements lanthanum, aluminium, 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.

Background

LSAT was originally developed as a substrate for the growth of high T_c cuprate superconductors thin films, mostly of yttrium barium copper oxide (YBCO), for microwave device applications. The motivation for its development was to create a lattice-matched substrate with a similar thermal expansion coefficient and no structural phase transition over a wide temperature range, spanning from the high temperatures used for the growth of cuprates, to the cryogenic temperatures where they are superconducting.^[1]

Properties

LSAT has a Mohs hardness of 6.5, placing it between quartz and the mineral feldspar. Its relative dielectric constant is ~22 and it has a thermal expansion coefficient of 8~10×10⁻⁶/K. The thermal conductivity of LSAT is 5.1 Wm⁻¹K⁻¹.^[2]^[3] LSAT's (cubic) lattice parameter of 3.868 Å makes it compatible for the growth of a wide range of perovskite oxides with a relatively low strain.^{[ citation needed ]}

LSAT's melting temperature of 1,840C is lower compared to similar alternative substrates, such as LaAlO₃. This property enables the growth of LSAT single crystals using the Czochralski process (CZ), which has commercial advantages.^[4]

Uses

LSAT is primarily used in its single crystal form, typically as thin (≤1 mm) wafers. These wafers are used as a common substrate for epitaxial growth of thin films. LSAT substrates are popular for epitaxial oxides and their heterostructures, often in the study of electron correlation phenomena. Typical materials grown on LSAT substrates include strontium titanate (SrTiO₃), cuprate superconductors (such as YBCO), iron-based superconductors (iron-pnictides), rare-earth manganites, rare-earth nickelates and others. Semiconductors such as gallium nitride can also be grown on LSAT.^[5]

LSAT's usefulness as a substrate for the growth of such films stems from its high chemical and thermal stability, and very low electrical conductivity. The growth conditions for such epitaxial layers can cause some substrates to form high densities of defects that can alter their properties. One example is the tendency of strontium titanate to form oxygen vacancy defects under high temperatures in high vacuum. These defects result in considerable variations of its properties, including the increase of electrical conductivity and optical opacity. LSAT on the other hand, is stable in both oxidizing and fairly reducing environments in high temperatures, thus enabling a larger window for the processing and growth conditions.^{[ citation needed ]}

Related Research Articles

Unconventional superconductors are materials that display superconductivity which does not conform to conventional BCS theory or its extensions.

High-temperature superconductors are defined as materials with critical temperature above 77 K, the boiling point of liquid nitrogen. They are only "high-temperature" relative to previously known superconductors, which function at even colder temperatures, close to absolute zero. The "high temperatures" are still far below ambient, and therefore require cooling. The first break through of high-temperature superconductor was discovered in 1986 by IBM researchers Georg Bednorz and K. Alex Müller. Although the critical temperature is around 35.1 K, this new type of superconductor was readily modified by Ching-Wu Chu to make the first high-temperature superconductor with critical temperature 93 K. Bednorz and Müller were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high- $T$ _c materials are type-II superconductors.

<span class="mw-page-title-main">Perovskite (structure)</span> Type of crystal structure

A perovskite is any material with a crystal structure following the formula ABX₃, which was first discovered as the mineral called perovskite, which consists of calcium titanium oxide (CaTiO₃). The mineral was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and named after Russian mineralogist L. A. Perovski (1792–1856). 'A' and 'B' are two positively charged ions (i.e. cations), often of very different sizes, and X is a negatively charged ion (an anion, frequently oxide) that bonds to both cations. The 'A' atoms are generally 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. Additional perovskite forms may exist where either/both the A and B sites have a configuration of A1_x-1A2_x and/or B1_y-1B2_y and the X may deviate from the ideal coordination configuration as ions within the A and B sites undergo changes in their oxidation states.

Yttrium barium copper oxide (YBCO) is a family of crystalline chemical compounds that display high-temperature superconductivity; it includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen at about 93 K.

<span class="mw-page-title-main">Strontium titanate</span> Chemical compound

Strontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO₃. 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. 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.

<span class="mw-page-title-main">Lead zirconate titanate</span> Chemical compound

Lead zirconate titanate, also called lead zirconium titanate and commonly abbreviated as PZT, is an inorganic compound with the chemical formula Pb[Zr_xTi_1−x]O₃(0 ≤ x ≤ 1). 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.

<span class="mw-page-title-main">Barium titanate</span> Chemical compound

Barium titanate (BTO) 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, pyroelectric, and piezoelectric ceramic material that exhibits the photorefractive effect. It is used in capacitors, electromechanical transducers and nonlinear optics.

Bismuth strontium calcium copper oxide (BSCCO, pronounced bisko), is a type of cuprate superconductor having the generalized chemical formula Bi₂Sr₂Ca_n−1Cu_nO_2n+4+x, with n = 2 being the most commonly studied compound (though n = 1 and n = 3 have also received significant attention). Discovered as a general class in 1988, BSCCO was the first high-temperature superconductor which did not contain a rare-earth element.

Bismuth ferrite (BiFeO₃, also commonly referred to as BFO in materials science) is an inorganic chemical compound with perovskite structure and one of the most promising multiferroic materials. The room-temperature phase of BiFeO₃ is classed as rhombohedral belonging to the space group R3c. It is synthesized in bulk and thin film form and both its antiferromagnetic (G type ordering) Néel temperature (approximately 653 K) and ferroelectric Curie temperature are well above room temperature (approximately 1100K). Ferroelectric polarization occurs along the pseudocubic direction ( $) with a magnitude of 90-95 μC/cm 2 .$

Karl Alexander Müller was a Swiss physicist and Nobel laureate. He received the Nobel Prize in Physics in 1987 with Georg Bednorz for their work in superconductivity in ceramic materials.

Lanthanum strontium manganite (LSM or LSMO) is an oxide ceramic material with the general formula La_1−xSr_xMnO₃, where x describes the doping level.

Cuprate superconductors are a family of high-temperature superconducting materials made of layers of copper oxides (CuO₂) alternating with layers of other metal oxides, which act as charge reservoirs. At ambient pressure, cuprate superconductors are the highest temperature superconductors known. However, the mechanism by which superconductivity occurs is still not understood.

<span class="mw-page-title-main">Perovskite</span> Oxide mineral

Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula CaTiO₃). Its name is also applied to the class of compounds which have the same type of crystal structure as CaTiO₃, known as the perovskite structure, which has a general chemical formula A²⁺B⁴⁺(X²⁻)₃. Many different cations can be embedded in this structure, allowing the development of diverse engineered materials.

LSAT may refer to:

<span class="mw-page-title-main">Superconducting wire</span> Wires exhibiting zero resistance

Superconducting wires are electrical wires made of superconductive material. When cooled below their transition temperatures, they have zero electrical resistance. Most commonly, conventional superconductors such as niobium–titanium are used, but high-temperature superconductors such as YBCO are entering the market.

Distrontium ruthenate, also known as strontium ruthenate, is an oxide of strontium and ruthenium with the chemical formula Sr₂RuO₄. It was the first reported perovskite superconductor that did not contain copper. Strontium ruthenate is structurally very similar to the high-temperature cuprate superconductors, and in particular, is almost identical to the lanthanum doped superconductor (La, Sr)₂CuO₄. However, the transition temperature for the superconducting phase transition is 0.93 K (about 1.5 K for the best sample), which is much lower than the corresponding value for cuprates.

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.

Lanthanum ytterbium oxide is a solid inorganic compound of lanthanum, ytterbium and oxygen with the chemical formula of LaYbO₃. This compound adopts the Perovskite structure.

Mixed conductors, also known as mixed ion-electron conductors(MIEC), are a single-phase material that has 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

↑ B.C. Chakoumakos (1998). "Thermal expansion of LaAlO₃ and (La,Sr)(Al,Ta)O₃ substrate materials for superconducting thin-film device applications" (PDF). Journal of Applied Physics . 83 (4): 1979–1982. Bibcode:1998JAP....83.1979C. doi:10.1063/1.366925.
↑ LSAT properties Archived 2014-06-27 at archive.today from the manufacturer Toplent Photonics Componenets
↑ LSAT properties from the manufacturer Sigma-Aldrich
↑ LSAT specs and information from the manufacturer MTI Corp.
↑ W. Wang; et al. (2013). "Growth and characterization of GaN-based LED wafers on La_0.3Sr_1.7AlTaO₆ substrates". Journal of Materials Chemistry C . 1 (26): 4070. doi:10.1039/C3TC00916E.

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[1] B.C. Chakoumakos (1998). "Thermal expansion of LaAlO₃ and (La,Sr)(Al,Ta)O₃ substrate materials for superconducting thin-film device applications" (PDF). Journal of Applied Physics . 83 (4): 1979–1982. Bibcode:1998JAP....83.1979C. doi:10.1063/1.366925.

[2] LSAT properties Archived 2014-06-27 at archive.today from the manufacturer Toplent Photonics Componenets

[3] LSAT properties from the manufacturer Sigma-Aldrich

[4] LSAT specs and information from the manufacturer MTI Corp.

[5] W. Wang; et al. (2013). "Growth and characterization of GaN-based LED wafers on La_0.3Sr_1.7AlTaO₆ substrates". Journal of Materials Chemistry C . 1 (26): 4070. doi:10.1039/C3TC00916E.

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