Phase Composition and the Thermoelectric Properties Material System Pb-Ag-Te

Abstract

In this work the phase composition and the thermoelectric properties of doped silver lead telluride with impurity concentration of 0.3, 0.5, 1.0 at.% and solid solutions Pb18-xAg2Te20 (x = 0, 0.5, 1.0), Pb17Ag3Te20 are researched. Synthesis of materials carried out in evacuated quartz ampoules. The resulting ingots ground in an agate mortar and highlighting fraction size (0.05 - 0.5) mm and pressed under pressure of 1.5 GPa. The obtained samples with d = (5-8) mm and h ≈ (8-12) mm subjected to additional annealing. Based on X-diffraction studies found that the introduction of impurities in silver in PbTe samples are shown traces of phase pure lead. For all samples of solid solutions Pb-Ag-Te in diffraction pattern observed additional phase and Te Ag10,6Te7. The coefficient of thermal emf samples containing impurities 0.3 and 0.5 at. % Ag are almost identical and monotonically decreasing values of 500 mV / K at 100 C, to values of 350 mV / s at 350 C. The temperature dependence of the thermopower samples containing impurities 1 at. % Ag characterized by nonmonotonic dependence with a maximum of 400 mV / s at 200 C. Thermal conductivity increases with little increase in the number of impurities. Unlike the doped material for all formulations investigated Pb18-xAg2 (3) Te20 (x = 0, 0.5, 1.0) was obtained stable-type conductivity. The conductivity of the material is higher compared to the doped material. There is a marked increase in the value of σ with reduction of lead in solution, although hol by measuring the concentration of media virtually unchanged. Thermopower factor for all compositions Pb18-x Ag2Te20 is almost the same and is ≈300 mV / s at 300 C. Thermal conductivity decreases with the decrease of lead in solution, which can be explained by the increase in the number of vacancies of lead, which scattered phonons. Lowest value of k samples characterized Pb17Ag3Te20. It is important that this sample is themost intense peaks of additional phases Ag 10,6 Te7.