THERMOELECTRICITY OF 2-PHASE MIXTURES, EACH WITH A DIFFERENT TYPE CHARGE-CARRIER, P-NIO N-ZNO/

This paper concerns whether the simple mixing rule for thermopower, th eta = Sigma t(k) theta(k) works for a heterogeneous, two-phase mixture , each with different types of charge carriers (k), where t(k) and the ta(k) are the transference number and thermopower for the kth-type car riers, respectively. We examined the thermopower of p-NiO/n-ZnO two-ph ase mixtures with an artificial series or parallel configuration and a real polycrystalline configuration as a function of the mixture compo sition, temperature, and microstructure. It was found that the mixing rule is generally valid for mixtures with the minority phase along gra in boundaries. The anomalous, repetitive transitions from n-to-p-to-n- type with increasing temperature are attributed alternations of the pr edominant conduction paths with temperature. This mixing rule is compa red with conventional theories of the effective thermopower of mixture s.