A2Zr2O7 (A = Nd, Sm, Gd, Yb) zirconate ceramics with pyrochlore-type structure for high-temperature negative temperature coefficient thermistor

The aim of this paper is to present a novel negative temperature coefficient (NTC) thermistor based on A 2 Zr 2 O 7 (A = Nd, Sm, Gd, Yb) zirconate ceramics with pyrochlore-type structure for high-temperature application. The zirconate ceramics were synthesized via a solid-state reaction method where rare-earth oxides and ZrO 2 were used as starting materials. The physical structures were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. It was confirmed that Nd 2 Zr 2 O 7 and Sm 2 Zr 2 O 7 are pyrochlore phases, while Yb 2 Zr 2 O 7 and Gd 2 Zr 2 O 7 are defect fluorite phases. The electrical property investigated by using resistance–temperature measurements demonstrated that the prepared A 2 Zr 2 O 7 zirconate ceramics exhibit a typical characteristic of NTC over a wide temperature range between 673 and 1273 K. Particularly, A 2 Zr 2 O 7 , in addition to having high activation energy to ensure better sensitivity, can still maintain higher resistivity under high-temperature environments. Furthermore, the resistivity of A 2 Zr 2 O 7 is almost independent of the change in oxygen partial pressure. These properties are superior to the classical spinel-type or perovskite-type NTC thermistor, providing valuable information to explore new NTC thermistor for high-temperature applications.