High-entropy (Ca0.5Ce0.5)(Nb0.25Ta0.25Mo0.25W0.25)O4 scheelite ceramics with high-temperature negative temperature coefficient (NTC) property for thermistor materials

(Ca0.5Ce0.5)(Nb0.25Ta0.25Mo0.25W0.25)O4 high-entropy ceramics with single scheelite phase structure were synthesized by solid-state reactions under a reducing atmosphere of argon, and their high-temperature electrical properties were investigated. The single scheelite phase of high-entropy ceramics is fabricated at a sintering temperature of 1300 °C, and grain sizes as well as relative densities of high-entropy ceramics increase with the increase of sintering temperature. High-entropy ceramics sintered at 1300 °C and 1400 °C exhibit excellent negative temperature coefficient (NTC) property within an ultrawide temperature range of 150 °C-1200 °C. Ceramic samples sintered under Ar tend to have lower activation energy, for the higher Ce3+ contents they possess than those sintered under air are in favor of increasing their polaron concentration. In comparison with conventional scheelite ceramics, high-entropy scheelite ceramics have a unitary NTC mechanism within a wider temperature range and a better aging property, for their crystal structure is stabilized by high-entropy effect at higher temperature.