PHYSICOCHEMICAL PROPERTIES OF SOLID SOLUTIONS BASED ON LEAD AND GALLIUM CHALCOGENIDES

This article investigates the physical-chemical properties of lead and gallium chalcogenide solid solutions, specifically Pb1-xGaxTe and Pb1-xGexTe, which are crucial for the advancement of thermoelectric devices. The research is motivated by the escalating global demand for alternative energy sources and energy-saving technologies, particularly for autonomous power systems (space, oceanographic, meteorological stations) and compact cooling/heating applications. The study aimed to examine the parameters of these compounds, optimize their synthesis, and broaden their application scope, with an emphasis on reducing manufacturing costs and complexity. The synthesis of Pb1-xGexTe was conducted in an oscillating furnace using high-purity components and controlled pressure, effectively addressing conductivity instability issues stemming from non-uniform germanium distribution and an anomalous temperature dependence of the equilibrium constant. The resulting Pb1-xGexTe (x<0.1) samples exhibited stable n-type conductivity with a thermo-EMF coefficient of 300 µV/K and significantly enhanced mechanical strength. For Pb1-xGaxTe, the donor effect of gallium was established: at concentrations up to 0.5 mol.% GaTe, a sharp decrease in electrical conductivity and a change in thermo-EMF sign were observed, attributed to gallium atoms substituting lead vacancies. At higher concentrations (>0.5 mol.% GaTe), the predominant mechanism involves the substitution of single-charged gallium ions into octahedral voids and the incorporation of triple-charged ions into interstitial sites, further reducing cationic sublattice vacancies and hole concentration. The findings substantially advance the understanding of defect chemistry and conduction mechanisms in these materials, paving the way for the development of high-performance thermoelectric devices with improved operational characteristics.