Physicochemical interactions in the GeSb$_{2}$Te$_{4}$–PbSb$_{2}$Te$_{4}$ System

For the first time, the GeSb$_{2}$Te$_{4}$–PbSb$_{2}$Te$_{4}$ section of the GeTe–Sb$_{2}$Te$_{3}$–PbTe quasi-ternary system is investigated by complex methods of physicochemical analysis (differential thermal, microstructural, and X-ray phase analysis with microhardness measurement and density determination) and the phase diagram is constructed. It is established that the section is a partially quasi-binary section of the GeTe–Sb$_{2}$Te$_{3}$–PbTe quasi-ternary system. The GeSb$_{2}$Te$_{4}$-based region of the solid solution (15 mol% PbSb$_{2}$Te$_{4}$) is revealed. The congruently melting compound GePbSb$_{4}$Te$_{8}$ is formed with the ratio of the initial components 1:1. Single crystals of the GePbSb$_{4}$Te$_{8}$ quaternary compound are formed by the method of chemical transport reactions. The unit-cell parameters of the GePbSb$_{4}$Te$_{8}$ compound, which crystallizes in the orthorhombic crystal system, are determined: $a$ = 5.06 $\mathring{\mathrm{A}}$, $b$ = 9.94 $\mathring{\mathrm{A}}$, and $c$ = 11.62 $\mathring{\mathrm{A}}$. It is established by investigation of the temperature dependences of certain electrical parameters of the GePbSb$_{4}$Te$_{8}$ compound and (GeSb$_{2}$Te$_{4}$)$_{x}$ (PbSb$_{2}$Te$_{4}$)$_{1-x}$ solid solution that the alloys have $p$-type conductivity.