New negative temperature coefficient ceramics in Ca0.9Y0.1MoO4–CeNbO4 system

Abstract

The Ca0.9Y0.1CeNbMoO8 compounds are the solid solutions of Ca0.9Y0.1MoO4 and CeNbO4, and have a potential in the high temperature thermistor application. A concept has been proposed to adjust the negative temperature coefficient (NTC) properties of these thermistors by increasing the content of CeNbO4. The structure of as-sintered Ca0.9Y0.1MoO4–xCeNbO4 ceramics is a single Ca0.9Y0.1MoO4 phase at x < 2.5, while the CeNbO4 phase begins to appear at x ≥ 2.5. The thermistor samples have remarkable NTC characteristics in the temperature of 50–700 °C. The resistivity, β300/500℃ constant and activation energy all decrease with increasing CeNbO4. The increase of Ce3+ content proved by XPS analysis is the reason for the decrease of the resistivity. The β300/500℃ and Ea values of the NTC thermistors are in the range of 5768–6583 K, 0.497–0.568 eV, respectively. After annealing at 500 °C in air for 200 h, the coefficient of aging (ΔR/R) is less than 2%, suggesting the materials show excellent stability.