Mixed (ionic and hole) conductivity of Tl3VS4 crystals

A model of mixed (ionic and hole) conductivity in Tl3VS4 crystals at close-to-room temperatures is proposed. The significant fraction of the ionic conductivity component (approximately 70 percent of the total conductivity) is explained by the nonstoichiometric electrically active thallium vacancies, whose acceptor levels provide p-type conductivity. The characteristic time dependence of the voltage developing across a sample due to its polarization and depolarization is described using the diffusion theory of mixed conductivity previously developed by Yokota. The charge transport phenomena in Tl3VS4 are studied experimentally, and the data are processed according to the theoretical model.