THERMOPOWER AND ELECTRICAL-CONDUCTIVITY OF SINGLE-CRYSTAL AND POLYCRYSTALLINE COO

Comparative stuates of both electrical conductivity and thermopower (S eeback effect) were carried out for undoped Co1-yO involving both sing le crystal and polycrystalline specimens within the temperature range 1223-1473 K and under oxygen partial pressure range 10-10(5) Pa. It wa s observed that the reciprocal of oxygen pressure exponent determined by thermopower (n(alpha)) and electrical conductivity (n(sigma)) for b oth single crystal and polycrystalline CoO increases with temperature. The parameter n(alpha) assumes much higher values than n(sigma) for b oth specimens. The mobility of electron holes increases with nonstoich iometry (y) for both the single crystal and the polycrystalline specim en. Based on the electrical conductivity data on temperatures it was c oncluded that conduction in CoO occurs according to the hopping model rather than the band model. The effect of p(O2) on the exponent of the oxygen pressure dependence have been considered in terms of interacti ons between the defects in this region.