Electrical properties of p-NiO/n-ZnO two-phase mixtures

Thermopower and electrical conductivity of the two-phase mixtures of semiconducting oxides having different types of majority charge carriers, (1 - x)NiO-xZnO system, were measured as functions of composition (0 less than or equal to x less than or equal to 1), topography of second phase (morphology, thickness of intergranular phase) and temperature (25 less than or equal to T/ degree C less than or equal to 1050). Thermopower varies from p- to n-type with respect to composition and temperature. Especially, p-n transition temperature depends on the second phase volume fraction and/or thickness of intergranular phase. The variations of electrical properties of p-n mixtures with respect to composition, temperature and microstructure are discussed by considering the existence of highly resistive charge depletion region along the p-n heterojunctions.