Effect of oxygen partial pressure during firing on electrical properties of sintered body composed of Mn1.5CoNi0.5O4

The effect of P-O2 during the oxidation of a sintered body with a molar rat io of Mn : Co : Ni = 3 : 2 : 1 on conversion into a cubic spinel-type oxide was investigated. Moreover, the electrical properties of the sintered body with a monophase cubic spinet structure were evaluated in atmospheres with various P-O2 values. A sintered body of monophase spinet-type oxide. Mn1.5 CoNi0.5O4, was successfully obtained by heating a mixture of nitrates at 14 00 degreesC in argon, followed by cooling to 1100 degreesC and holding at t hat temperature for over 168 h at P-O2 = 0.40 atm, or for over 48 h in the P-O2 range from 0,55 to 1.00 atm. The electrical conductivity, sigma, of th e specimens oxidized at P-O2 of 0.40 to 1.00 atm increased exponentially wi th increasing temperature. In the region of 0.40 less than or equal to P-O2 (atm) : 0.85, or increased with increasing P-O2 All of the specimens oxidi zed at P-O2 of 0.40 to 1.00 atm revealed p-type semiconductor properties, b ecause the Seebeck coefficients were all positive, The P-O2 dependence of a was thought to be dependent on the existence ratio of Mn3+ to Mn4+ in octa hedral sites. The conduction was considered to be controlled by a small pol aron hopping mechanism.