Microstructure and Electrical Properties of Mn_(2.25-x)Ni_(0.75)Co_xO_4 Thermistor Ceramics

A series of composite of the negative temperature coefficient(NTC) powders of Mn2.25-xNi0.75CoxO4(0.8≤x≤1.2) materials were prepared via solid-state method.The particle size of calcined powders,ceramics phase structure,morphology and electrical properties were characterized by laser particle size analyzer,XRD,SEM and electrical measurements,respectively.The results show that when the Mn2.25-xNi0.75CoxO4 ceramics sintered at 1130?1230℃,their characteristic parameters B25/50 value are found to be in the range of 3487K to 4455K and their electrical resistivi-ties ρ25℃ are 1998 Ω?cm to 203617 Ω?cm.The B25/50 value and ρ25℃ first increases and then decreases as the Co content increases.This means that electrical resistivity and B value of Mn2.25-xNi0.75CoxO4 ceramics could be adjusted to the de-sired values and this ternary system can be considered as the advanced semi-conducting materials for NTC thermistor applications.