PHYSICAL AND CHEMICAL PROPERTIES, CONDUCTIVITY TYPE AND THERMOELECTRIC FORSE IN SOLID SOLUTIONS CEXSN1-XSE
The thermoelectrically moving force (thermo-emf) S, conductivity in CexSn1-xSe solid solutions (x = 0.00-0.035) in the temperature range of 80-400 K were studied. A change in the sign of S from p- to n-type and a decrease in σ with increasing Ce were found. The activation energies of impurity regions are estimated. The behavior of S (T) and σ (T) is due to an increase in the defectiveness of the crystal lattice. In the composition of CexSn1-xSe (x = 0.00-0.035), the value of thermoelectric power with (Ѕ ˃ 0) decreases and at x = 0.025 it changes sign to negative. A similar decrease in electrical conductivity is observed up to x = 0.020; then, with an increase in the Ce content, it increases. Apparently, such changes in Ѕ and σ are due to the process of filling tin vacancies and a change in anti-structural defects of selenium. This leads to a decrease in the concentration of charge carriers. With a further increase in the Ce content, the formation of anti-structural defects almost does not occur, but charge carriers of a different type appear, which leads to an increase in electrical conductivity. This behavior of Ѕ with a change in the Ce content in CexSn1-xSe can be explained, since in SnSe there are mainly two types of defects: Sn vacancies and anti-structural defects of selenium, with some of the neutral Sn atoms located in the interstices of the SnSe lattice.