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By differential thermal analysis, a concentration field suitable for the growth of Zr, Mg co-doped strontium hexagallate crystals was observed that corresponds well with known experimental results. It was shown that the melting point of doped crystal is ca. 60 K higher than that of undoped crystals. This higher melting points indicate hexagallate phase stabilization by Zr, Mg co-doping and increase the growth window of (Mg,Zr):SrGa12O19, compared to undoped SrGa12O19 that grows from SrO–Ga2O3 melts. [ABSTRACT FROM AUTHOR]

Large bulk LaInO3 single crystals are grown from the melt contained within iridium crucibles by the vertical gradient freeze (VGF) method. The obtained crystals are undoped or intentionally doped with Ba or Ce, and enabled wafer fabrication of size 10 × 10 mm2. High melting point of LaInO3 (≈1880 °C) and thermal instability at high temperatures require specific conditions for bulk crystal growth. The crystals do not undergo any phase transition up to 1300 °C, above which a noticeable thermal decomposition takes place. The good structural quality of the crystals makes them suitable for epitaxy. The onset of strong optical absorption shows orientation‐dependent behavior due to the orthorhombic symmetry of the LaInO3 crystals. Assuming direct transitions, optical bandgaps of 4.35 and 4.39 eV are obtained for polarizations along the [010] and the [100], [001] crystallographic directions, respectively. There is an additional weak absorption in the range between 2.8 and 4 eV due to oxygen vacancies. Density‐functional‐theory calculations support the interpretation of the optical absorption data. Cathodoluminescence spectra show a broad, structured emission band peaking at ≈2.2 eV. All bulk crystals are electrically insulating. The relative static dielectric constant is determined at a value of 24.6 along the [001] direction. [ABSTRACT FROM AUTHOR]

Cubic rare‐earth sesquioxide crystals are strongly demanded host materials for high power lasers, but due to their high melting points investigations on their thermodynamics and the growth of large‐size crystals of high optical quality remain a challenge. Detailed thermal investigations of the ternary system Lu2O3–Sc2O3–Y2O3 revealing a large range of compositions with melting temperatures below 2200°C and a minimum of 2053°C for the composition (Sc0.45Y0.55)2O3 are presented. These reduced temperatures enable for the first time the growth of high optical quality mixed sesquioxide crystals with disordered structure by the conventional Czochralski method from iridium crucibles. An (Er0.07Sc0.50Y0.43)2O3 crystal is successfully grown and characterized with respect to its crystallographic properties as well as its composition, thermal conductivity and optical absorption in the 1 µm range. [ABSTRACT FROM AUTHOR]

Abstract: The growth of ZnO bulk crystals from the melt is difficult due to the high melting point of the material (T m =1975°C), requiring the use of Ir crucibles, and its thermal decomposition upon heating. A thermodynamic analysis shows that the oxygen partial pressure in the surrounding vapour phase should be as low as possible during the heating cycle at lower temperatures in order to avoid the oxidation of Ir to IrO2. Approaching the ZnO melting point, however, higher oxygen pressure is required for suppressing the ZnO decomposition, while IrO2 decomposes in the elements. The required increasing oxygen supply with increasing temperature can be accomplished by the addition of CO2 to the gas atmosphere. Experimental results prove the correctness of these results. In a Bridgman-like process ZnO boules are obtained that consist of a few large grains with cm dimensions. [Copyright &y& Elsevier]

Abstract: Zinc oxide single crystals were obtained by solidification of a melt contained in an iridium crucible. To the authors knowledge this is the first report on crystal growth of zinc oxide from the melt using an inductively heated metal crucible. This proves that under particular conditions metals are capable of withstanding liquid zinc oxide at high temperatures. Optical microscopy as well as X-ray rocking curve measurements reveal the high crystalline quality of the wafers with full-width at half-maximum values of 22arcsec. Annealing of as-grown samples was observed to have a big influence on optical properties. [Copyright &y& Elsevier]

Cubic rare‐earth sesquioxide crystals are strongly demanded host materials for high power lasers, but due to their high melting points investigations on their thermodynamics and the growth of large‐size crystals of high optical quality remain a challenge. Detailed thermal investigations of the ternary system Lu2O3–Sc2O3–Y2O3 revealing a large range of compositions with melting temperatures below 2200°C and a minimum of 2053°C for the composition (Sc0.45Y0.55)2O3 are presented. These reduced temperatures enable for the first time the growth of high optical quality mixed sesquioxide crystals with disordered structure by the conventional Czochralski method from iridium crucibles. An (Er0.07Sc0.50Y0.43)2O3 crystal is successfully grown and characterized with respect to its crystallographic properties as well as its composition, thermal conductivity and optical absorption in the 1 µm range. [ABSTRACT FROM AUTHOR]

• Perovskite solid solutions can produce indifferent points with a congruently melting minimum. • Pair selection criteria include a Goldschmidt perovskite tolerance factor close to unity. • Seven solid solution pairs with cubic crystal structure were identified in this study. • These materials have favorable lattice parameters for perovskite substrate applications. • Czochralski/Bridgman growth show that sodium evaporation and attendant hazards are a problem. Single-crystal substrate materials with crystal structures and lattice parameters matching a desired epitaxial film are an enabling technology for many critical materials. Such substrates are best grown by bulk techniques that benefit from the substrate material being congruently melting. The shortage of congruently melting perovskites in critical lattice parameter ranges has been addressed herein by a search for new congruently melting compositions. A solid solution of two perovskites can be congruently melting at a minimum temperature under specified thermodynamic conditions where the coefficient matrix has a zero determinant. This is called an indifferent point. A wide variety of perovskite solid solutions were investigated to identify compounds that have an indifferent melting minimum and a cubic crystal structure with favorable lattice constants in the range of 0.390–0.412 nm. Solid solution pairs that form such indifferent points include, but are not limited to, seven compositions identified in this study. The lattice parameters of the new materials show a broad range of desirable lattice constants. A perovskite tolerance factor close to unity gave a favorable contribution to the free energy and makes a cubic crystal structure favorable. These solid solutions constitute a broad and important class of compounds not previously anticipated. The only significant drawback is the high vapor pressure of sodium, which is present in most of these materials and requires special growth conditions and equipment for safety. [ABSTRACT FROM AUTHOR]

In the course of development of transparent semiconducting oxides (TSOs) we compare the growth and basic physical properties bulk single crystals of ultra-wide bandgap (UWBG) TSOs, namely β-Ga 2 O 3 and Ga-based spinels MgGa 2 O 4 , ZnGa 2 O 4 , and Zn 1-x Mg x Ga 2 O 4. High melting points of the materials of about 1800 -1930 °C and their thermal instability, including incongruent decomposition of Ga-based spinels, require additional tools to obtain large crystal volume of high structural quality that can be used for electronic and optoelectronic devices. Bulk β-Ga 2 O 3 single crystals were grown by the Czochralski method with a diameter up to 2 inch, while the Ga-based spinel single crystals either by the Czochralski, Kyropoulos-like, or vertical gradient freeze / Bridgman methods with a volume of several to over a dozen cm3. The UWBG TSOs discussed here have optical bandgaps of about 4.6 - 5 eV and great transparency in the UV / visible spectrum. The materials can be obtained as electrical insulators, n -type semiconductors, or n -type degenerate semiconductors. The free electron concentration (n e) of bulk β-Ga 2 O 3 crystals can be tuned within three orders of magnitude 1016 - 1019 cm−3 with a maximum Hall electron mobility (μ) of 160 cm2V−1s−1, that gradually decreases with n e. In the case of the bulk Ga-based spinel crystals with no intentional doping, the maximum of n e and μ increase with decreasing the Mg content in the compound and reach values of about 1020 cm−3 and about 100 cm2V−1s−1 (at n e > 1019 cm−3), respectively, for pure ZnGa 2 O 4. [ABSTRACT FROM AUTHOR]