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Laser‐flash measurements of the thermal conductivity λ(hkl)$\lambda _{(hkl)}$ of Czochralski‐grown β‐Ga2O3 single crystals are reported perpendicular to four independent crystallographic lattice planes (hkl)=(2¯01)$(hkl)=(\bar{2}01)$, (010), (001), and (100) between room temperature and 1200 K. λ is represented by a symmetric tensor of rank 2 and has four independent components. Tensor components λ11=λ(100)=12.13$\lambda _{11}=\lambda _{(100)}=12.13$ W m−1 K−1 and λ22=λ(010)=24.26$\lambda _{22}=\lambda _{(010)}=24.26$ W m−1 K−1 (values for 300 K) can be directly measured. λ33=14.09$\lambda _{33}=14.09$ W m−1 K−1 and λ13=−0.992$\lambda _{13}=-0.992$ W m−1 K−1, instead, are obtained by combining λ(001)=13.53$\lambda _{(001)}=13.53$ W m−1 K and λ(2¯01)=14.33$\lambda _{(\bar{2}01)}=14.33$ W m−1 K. The crystallographic b⃗$\vec{b}$‐axis is the direction with the highest thermal conductivity, λ22. The thermal conductivity assumes its lowest value (11.73 W m−1 K−1) in a direction close to the crystallographic a⃗$\vec{a}$‐axis. However, this direction does not coincide with a⃗$\vec{a}$, and changes with temperature. [ABSTRACT FROM AUTHOR]

The phase relations in the system with the overall chemistry Nd2O3:Lu2O3 around 1:1 were investigated by x-ray diffraction (XRD) of annealed powders and by differential thermal analysis (DTA). A mixture of rare earth oxide solid solutions in the cubic C and in the monoclinic B rare earth oxide structure was determined in the temperature range 1200 to 1650 °C. The C-phase is dominated by Lu content while the B-phase is Nd rich. With rising annealing temperature, the portion of Nd in the C-phase is increased and lowered for the B-phase. Different facilitation possibilities for P-NdLuO3 perovskite formation were discussed and examined but no evidence for stability of this phase could be found experimentally. Two thermal signals of phase transitions were detected. The first occurs at 1908 °C and disappears in second heating run if the temperature is raised too much. Furthermore, a second one was detected at 2121 °C. [ABSTRACT FROM AUTHOR]

Measurements of thermal diffusivity ? (using laser flash analysis) for temperatures from 100 °C to 1200 °C and of the inversion parameter x (using X-ray analysis) for the single crystal spinel MgGa2O4 have been performed. X-ray analysis showed a small change in x for samples annealed at 800 °C (x = 0.838) and 1200 °C (x = 0.834). Thermal diffusivity revealed a significant rise of ? for temperatures higher than 950 °C, deviating from the typical 1/T drop of ?. An additional systematic rise of ? with time is observed for temperatures between 950 °C and 1100 °C. A connection between cation disordering processes typical for spinels at elevated temperatures and the observed deviation of ? is proposed: Data indicate that cations changing their occupancy site at equilibration processes contribute significantly to ? and therefore represent a new type of heat transport. [ABSTRACT FROM AUTHOR]

The thermodynamic and crystallographic background for the development of substrate crystals that are suitable for the epitaxial deposition of biaxially strained functional perovskite layers is reviewed. In such strained layers the elastic energy delivers an additional contribution to the Gibbs free energy, which allows the tuning of physical properties and phase transition temperatures to desired values. For some oxide systems metastable phases can even be accessed. Rare‐earth scandates, REScO3, are well suited as substrate crystals because they combine mechanical and chemical stability in the epitaxy process with an adjustable range of pseudo‐cubic lattice parameters in the 3.95 to 4.02 Å range. To further tune the lattice parameters, chemical substitution for the RE or Sc is possible. [ABSTRACT FROM AUTHOR]

The ternary phase diagram of copper–iron–aluminium delafossite is established with FactSage calculations to improve the conditions for solution growth and the electrical conductivity of the transparent p‐type semiconductor copper–aluminium delafossite by addition of iron oxide. Initial growth experiments with the optical float zone method show that the growth of single crystals with commercially relevant dimensions is not expected in the near future. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including point of crystal defects in semiconductors and dielectrics, crystal growth twinning, and the properties and the production of crystalline materials.

The phase relations in the system with the overall chemistry Nd2O3:Lu2O3 around 1:1 were investigated by x-ray diffraction (XRD) of annealed powders and by differential thermal analysis (DTA). A mixture of rare earth oxide solid solutions in the cubic C and in the monoclinic B rare earth oxide structure was determined in the temperature range 1200 to 1650 °C. The C-phase is dominated by Lu content while the B-phase is Nd rich. With rising annealing temperature, the portion of Nd in the C-phase is increased and lowered for the B-phase. Different facilitation possibilities for P-NdLuO3 perovskite formation were discussed and examined but no evidence for stability of this phase could be found experimentally. Two thermal signals of phase transitions were detected. The first occurs at 1908 °C and disappears in second heating run if the temperature is raised too much. Furthermore, a second one was detected at 2121 °C. [ABSTRACT FROM AUTHOR]