Temperature dependence of the Hall coefficient and thermo-electromotive force in CdTl2Se4 monocrystals

Monocrystals of CdTl2Se4, with elementary cell parameters of a=4.28 A and c=6.67 A with a precision of +-0.02 A, were prepared by direct synthesis, directed crystallization, and gas-transport reactions. The thermo-emf and the Hall coefficient of CdTl2Se4 monocrystals were measured over a wide temperature range of 77 to 6500K. The measurements were made by the usual compensation method at constant current and for the Hall coefficient in a constant field strength of 2900 ergs. The results of the thermo-emf measurement and its temperature dependence showed that CdTl2Se4 monocrystals have a P type conductivity. No change in the sign of the thermo-emf for all samples in the temperature interval from 77 to 6500K was observed. In this temperature range the increase in conductivity of the current carrier in these compounds followed the law I varies as Tsup(0.45). At high temperatures, from 350 to 6500C, the dependence was more sharply defined and followed the law I varies as T-17. The chief mechanism of dispersion of vacancies in CdTl2Se4 is dispersion on ionzied impurities. At high temperatures, vacancies are dispersed chiefly by oscillations in the lattice. In the characteristic conductivity field the Hall coefficient, like the thermo-emf coefficient, decreases with increase in temperature, which is related to the vacancy concentration and dispersion