Thermoelectric effect in single-crystal cuprous oxide at high temperatures

Abstract

The thermoelectric effect in single-crystal cuprous oxide, measured at temperatures of 500° to 1130°C and oxygen pressures P of 160 to 2×10-6 Torr, was found always to be positive, indicating that the material is a p-type semiconductor in these ranges of conditions. Plots of the thermoelectric power Q vs 1/T at different constant oxygen pressures yield parallel straight Unes with a slope of 0.75 V. Plots of Q vs logP are mostly straight lines with slopes approximating (-2.3k) / (8q), in which k is Boltzmann's constant and q is the electronic charge. These results can be explained fairly satisfactorily in terms of a modified Wagner model for the defect structure of Cu2O and existing theories of the thermoelectric effect in semiconductors. It is assumed that the concentration of acceptors is a function of both the oxygen pressure and the temperature and that a gradient of acceptors exists along the temperature gradient. Thus, the model shows that the factor 8, originally obtained from conductivity measurements, should also be contained in the slope of Q vs logP. The slope of 0.75 V for the plot of Q vs 1/T can be related to the energy of creating an acceptor, i.e., a copper atom vacancy, plus the energy of ionizing this acceptor.