a To predict the grain boundaries composition of the nanocomposite thermoelectric IV-VI devices the oxidation processes in PbTe, SnTe, PbSe, SnSe and in some their solid solutions were studied. The initial oxidation stages were investigated by applying the potentiostatic anodic scan. The Auger electron spectroscopy, cathodoluminescence and X-ray diffraction were used to characterize the composition of the anodic and thermal oxides films. The obtained results demonstrate that the oxidation processes and the oxide composition are near the same at the substitution in the chalcogen sublattice (Te → Se), but they are strongly changed at the substitution in the metal sublattice (Pb → Sn). Under the same growing conditions, the grain boundaries will consist mainly of an amorphous tin oxide in SnTe and SnSe nanocomposites, and the ternary oxide forms the grain boundaries in PbTe and PbSe nanocomposites. In the solid solutions with the Sn occurrence in the metal sublattice tin oxidation becomes a prevailing process, even in case of low tin content.
High resolution in situ X-ray powder diffraction applying synchrotron radiation and differential thermal analysis/scanning calorimetry methods have been used to examine the pseudo-binary system PrAlO 3 -SmAlO 3 . Two kinds of solid solutions with rhombohedral and orthorhombic structure exist at room temperature. At elevated temperatures, a continuous phase transition P m3m ↔ R3c and a first-order transformation R3c ↔ P bmn occur in the two respective phases. A sequence of low-temperature phase transformations R3c ↔ Imma ↔ C2/m has been detected in Pr 1−x Sm x AlO 3 samples with x < 0.35. Based on in situ powder diffraction and differential thermal analysis/scanning calorimetry data, the phase diagram of the pseudo-binary system PrAlO 3 -SmAlO 3 has been constructed.
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