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Indium oxide as thin film and powder was prepared by the sol-gel method. The structural characterization of the film and powder showed that similar crystallite sizes are obtained in samples heat-treated at the same temperature. Thermo-gravimetric analysis and differential scanning calorimetry were performed in order to determine the activation energies of In 2 O 3 formation from precursors and subsequent crystal growth of both kinds of samples. Absorption measurements showed that the bandgap of the sol-gel polycrystalline films deposited on c-oriented sapphire is in excellent agreement with the one found in bulk and epitaxial indium oxide. The annealed films were found to be highly conductive with carrier concentration generally in excess of 10 19 cm − 3 . It was observed that the electrical characteristics of films annealed at 700 °C remained stable while those of films annealed at lower temperatures exhibited remarkable changes when measurements were repeated after seven months. [ABSTRACT FROM AUTHOR]

Small wüstite (Fe 1− x O) crystals were grown using the micro-pulling-down technique. Eutectoid decomposition of the grown crystals was suppressed by fast cooling associated with fast crystal pulling at a rate of 50 mm/min. Crystals grown at lower rates contained magnetite as a second phase indicating the beginning decomposition. Additionally, in those crystals the original wüstite of near-eutectoid composition ( x ≈ 0.05 ) was decomposed into two wüstite phases of which one was iron-poor, x ≈ 0.09 , the other instead iron-rich, near-stoichiometric, x ≈ 0.02 . [ABSTRACT FROM AUTHOR]

Abstract: The eutectic LiF–LiYF4 has been solidified by Bridgman and micro-pulling down (mPD) at pulling rates from 4 to 300mm/h. The microstructure changes from a coupled, interpenetrated-like one to macrofaceted colonies composed of an approximately triangular arrangement of LiF fibers inside the LiYF4 matrix as the pulling rate increases. The cross-over pulling rate is around 3 times larger for the mPD method, corresponding to its larger solidification gradient. The crystallographic growth direction of the matrix phase was found using EBSD. Effective medium estimations of the THz permittivity of the composite predict around the interphase phonon-polariton resonance (wavelength around 17.5μm) a small permittivity hyperbolic behavior specific of the ordered composite that is tolerant to different relative orientations. Water etching of polished cross-sections constitutes a very simple procedure to generate surface micro-holes of predefined size in the LiYF4 matrix. [Copyright &y& Elsevier]

Abstract: Solid solutions between zinc oxide and magnesium oxide containing up to 4at.% Mg were grown from the melt using a modified Bridgman technique. Chemical analysis (ICP-OES) and photoluminescence (PL) measurements revealed that the Mg concentration in the melt is larger compared with the starting material. This observation contradicts the commonly accepted assumption, that the ZnO–MgO phase diagram is of eutectic type. Peritectic melting of Zn-rich Zn1−x Mg x O can explain the new experimental results, and a new ZnO–MgO phase diagram is proposed. Furthermore a distribution coefficient for Mg of has been determined. [Copyright &y& Elsevier]

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]

[Display omitted] • Calcium carbonate in its various polymorphs reacts with sodium silicate solution. • This reaction results in formation of Na-containing C-S-H and sodium carbonates. • Formation of natron and C-S-H are observed at time of second calorimetric peak. • Formation of natron or thermonatrite depends upon the kinetics of reaction. • With higher reaction degree of calcite, formation of gaylussite is predicted. This article investigates the role of calcium carbonate minerals in an alkali-activated system through their reaction with sodium silicate solution. The early reaction kinetics and reaction products are investigated using isothermal conduction calorimetry, in-situ XRD and in-situ FTIR. Later reaction products are identified with thermodynamic modelling and analysis of the paste samples after 8 and 90 d using XRD, TGA, DSC and mass spectrometry. After a few hours of reaction, natron precipitates as the first crystalline carbonate phase, while changes in the connectivity of silicates are observed due to the precipitation of C-S-H, which may contain Na. After 8 and 90 d, C-S-H is observed together with thermonatrite instead of natron. It is shown that calcium carbonate is not just a filler in an alkali-activated system but can provide Ca to form C-S-H and can also enhance the availability of carbonate for the formation of alkali carbonates. [ABSTRACT FROM AUTHOR]

The pseudobinary system LaLuO 3 –LaScO 3 was explored in hopes of discovering new perovskite-type substrates with pseudocubic lattice parameters above 4 Å. A complete solid solution of the type (LaLuO 3 ) 1− x (LaScO 3 ) x forms between the end members LaLuO 3 and LaScO 3 , enabling large single crystals of (LaLuO 3 ) 1− x (LaScO 3 ) x to be grown from the melt. A single crystal with x ≈0.34 was demonstrated. Considering the maximum thermal load of the iridium crucibles appropriate for Czochralski growth of this solid solution, the theoretically maximum achievable x -value is ~0.67. Based on the phase diagram determined, it is anticipated that single crystals with pseudocubic lattice constants between 4.09 and 4.18 Å can be grown in this system by the Czochralski method. [ABSTRACT FROM AUTHOR]

The growth of bulkx β-Ga 2 O 3 single crystals by the Czochralski method is reported and discussed in terms of crucial growth conditions and correlated with basic electrical and optical properties of the obtained crystals. β-Ga 2 O 3 crystals have a tendency to a spiral formation due to free carrier absorption in the near infrared (NIR) wavelength range, which hampers radiative heat transfer through the growing crystal. Moderate or low free electron concentrations (<5×10 17 cm −3 ) lead to cylindrical crystals with a high crystallized fraction ( g ≥0.5). The use of a CO 2 -containing growth atmosphere provides oxygen partial pressures between 0.8 and 4.4×10 −2 bar that is sufficient to obtain cylindrical and semiconducting crystals. Doping with Sn increases the free electron concentration in the crystals to high values (~10 19 cm −3 ) that lead to an immediate spiral formation, while doping with Mg (>6 wt ppm) provides insulating crystals with reduced probability of the spiral formation. The estimated Mg equilibrium segregation coefficient across the liquid–solid interface is 0.10–0.12. Annealing of undoped crystals in an oxidizing atmosphere at temperatures ≥1200 °C for 20 h decreases the bulk free electron concentration by about one order of magnitude, while the crystal surface becomes insulating. However, Mg:β-Ga 2 O 3 crystals are insensitive to annealing in both oxygen- and hydrogen-containing atmospheres. The transmittance spectra showed a steep absorption edge at 260 nm and virtually full transparency in the visible and NIR wavelength range for low and moderate free electron concentrations. We also demonstrated the possibility of growing 2 in. diameter β-Ga 2 O 3 single crystals by the Czochralski method. The good crystal quality is evidenced by rocking curve FWHM values of below 50". We noted that most dislocations propagate parallel to (100) plane. Further, we also provide thermal properties of the crystals as a function of temperature. [ABSTRACT FROM AUTHOR]

Abstract: Homoepitaxial MgZnO thin films were grown from PLD targets with 1, 2, 4, and 10wt.% MgO content on ZnO-buffered ZnO(001) substrates. The resulting Mg content of the films was determined from the blue-shift of the excitonic peak in low-temperature photoluminescence spectra. With increasing Mg content a considerable increase of film mosaicity was observed from HR-XRD (002) rocking curves. Triple-axis reciprocal space maps of symmetric (002) and asymmetric (104) reflections show the structural development in terms of tilt and perpendicular and parallel strain. For more than 1% Mg the films exhibit increasing tensile out-of-plane strain. Very high electron mobilities of 200cm²/Vs at 300K and 900cm²/Vs at 65K were measured in the homoepitaxial MgZnO/ZnO thin films with free electron concentrations around 1018 and 1017 cm−3, respectively. The homoepitaxial ZnO template film deposited from a melt-grown ZnO single crystal as PLD target shows two orders of magnitude lower carrier concentration due to high compensation. [Copyright &y& Elsevier]

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]