Oxygen partial pressure dependency of electrical resistivity of MgCr2O4 with spinel type crystal structure

Stoichiometric oxide compound MgCr2O4 mere sintered with varying the holdin g time in the range 10 min-100 h. All the samples were single-phase spinel structure and p-type semiconductor. Oxygen partial pressure dependence of e lectrical resistivity was measured at 1000 degrees C in a Po, of 10(0)-10(- 18) atm. Oxygen partial pressure dependence of electrical resistivity was c learly divided into two groups according to the difference of holding time during sintering. The oxygen partial pressure dependence at longer holding time was well described by -2 ionized Cr vacancy model. However, the behavi or at shorter holding times could not be explained by invoking Cr vacancy m odels. Under very low oxygen partial pressure, resistivity of all samples s howed roughly the same value. It is shown that in such a low oxygen partial pressure atmosphere, Cr vacancy could not exist, and the sample conduction is dominated by an intrinsic conduction mechanism without formation of Cr vacancy.