CaMn0.05Zr0.95O3–NiMn2O4 composite ceramics with tunable electrical properties for high temperature NTC thermistors

A series of novel high temperature negative temperature coefficient (NTC) composite ceramics based on (1-x)CaMn0.05Zr0.95O3-xNiMn2O4 (x = 0, 0.1, 0.2, 0.3) were fabricated by using the solid-state method. The Rietveld refinement method and backscattered electron (BSE) image confirmed the absence of any other phase. The conduction mechanism of the composite ceramics was determined by analyzing the complex impedance and resistance-temperature characteristics, which could be related to the formation of a continuous Mn3+-O-Mn4+ network. The effect of spinel content on the high temperature stability was analyzed using aging tests. The ρ400°C, ρ700°C and B400/700 values of the NTC thermistors were determined to be 4.9 × 106–1.2 × 104, 1.4 × 105–0.8 × 103 Ω cm and 12739-5712 K, respectively. This indicated that the electrical properties could be tuned by adjusting the weight ratio of CaMn0.05Zr0.95O3 and NiMn2O4. The findings obtained in this study reveal that the composite NTC thermistor exhibits a good application potential at high temperatures and under harsh environments.