Microstructure and electrical properties of Ni1.0Mn2−xZrxO4 (0≤x≤1.0) negative temperature coefficient thermistors

The effect of the composition on the microstructure and electrical properties of Ni1.0Mn2−xZrxO4 (0≤x≤1.0) negative temperature coefficient (NTC) thermistors was studied. Major phases present in the sintered bodies of Ni1.0Mn2−xZrxO4 were the solid solutions of Ni–Mn–Zr oxides with a cubic spinel structure and the ZrO2 with a tetragonal structure. ZrO2 was formed by the partial decomposition or incomplete formation of the Ni–Mn–Zr oxides during sintering. The ZrO2 phase increased with an increase in the amount of added ZrO2. The relationship between log resistivity (log ρ) and the reciprocal of absolute temperature (1/T) of the prepared NTC thermistors was linear, indicative of NTC characteristics. The resistivity, B constant, and activation energy of the thermistors increased with an increase of ZrO2 content.