Preparation of ultra-fine cobalt–nickel manganite powders and ceramics derived from mixed oxalate

Abstract

Co 0.30Ni 0.66Mn 2.04O 4 negative temperature coefficient ceramics were derived from mixed oxalate Co 0.30Ni 0.66Mn 2.04(C 2O 4) 3· nH 2O. The mixed oxalate was synthesized by milling a mixture of cobalt acetate, nickel acetate, manganese acetate, and oxalic acid at room temperature. An ultra-fine Co 0.30Ni 0.66Mn 2.04O 4 powder was obtained by calcining the mixed oxalate in air at 800 °C for 3 h. The oxide powder compact was sintered at a relatively low temperature of 1100 °C for 5 h, achieving a relative density of ∼98%. The specific resistivity ρ 25 °C and the thermal constant B 25/85 °C were 765.2 Ω cm and 3604 K, respectively. The resistance drift after aging at 150 °C for 500 h was 1.5%.