Effect of Oxygen Partial Pressure during Firing on Electrical Properties of Sintered Body Composed of Mn1.5CoNi0.5O4

概要

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The effect of $P_{\text{O}_{2}}$ during the oxidation of a sintered body with a molar ratio of $\text{Mn}:\text{Co}:\text{Ni}=3:2:1$ on conversion into a cubic spinel-type oxide was investigated. Moreover, the electrical properties of the sintered body with a monophase cubic spinel structure were evaluated in atmospheres with various $P_{\text{O}_{2}}$ values. A sintered body of monophase spinel-type oxide, Mn1.5CoNi0.5O4, was successfully obtained by heating a mixture of nitrates at 1400°C in argon, followed by cooling to 1100°C and holding at that temperature for over 168 h at $P_{\text{O}_{2}}=0.40$ atm, or for over 48 h in the $P_{\text{O}_{2}}$ range from 0.55 to 1.00 atm. The electrical conductivity, $\sigma$, of the specimens oxidized at $P_{\text{O}_{2}}$ of 0.40 to 1.00 atm increased exponentially with increasing temperature. In the region of $0.40\leqq P_{\text{O}_{2}}(\text{atm})\leqq 0.85$, $\sigma$ increased with increasing $P_{\text{O}_{2}}$. All of the specimens oxidized at $P_{\text{O}_{2}}$ of 0.40 to 1.00 atm revealed p-type semiconductor properties, because the Seebeck coefficients were all positive. The $P_{\text{O}_{2}}$ dependence of $\sigma$ was thought to be dependent on the existence ratio of Mn3+ to Mn4+ in octahedral sites. The conduction was considered to be controlled by a small polaron hopping mechanism.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2001-08-15