Investigation of pyrochlore-type A2Sn2O7 (A = La, Nd, Sm, or Gd) ceramics as negative temperature coefficient thermistors for high-temperature application

This study puts forward a series of thermosensitive materials based on A2Sn2O7 (A = La, Nd, Sm, or Gd) ceramics for high-temperature applications. The A2Sn2O7 (A = La, Nd, Sm, or Gd) ceramics were synthesized following the solid-state route and characterized using techniques involving X-Ray diffraction, scanning electron microscopy, and Raman spectroscopy. It could be verified that the A2Sn2O7 (A = La, Nd, Sm, or Gd) ceramics had pyrochlore structures with relative densities ranging from 95.8 to 97.6%. The resistance-temperature measurements confirm that these ceramics have unique oxygen-insensitive negative temperature coefficient properties. The logarithm of resistivity depends on the reciprocal of temperature with excellent linearity over a wide temperature range of 400–1300 °C. A2Sn2O7 (A = La, Nd, Sm, or Gd) ceramics also exhibited well-ageing characteristics at their maximum upper applicable temperature of 1300 °C, in addition to the high resistivity and thermal constant B value that assured high accuracy. These properties outperformed those of the majority of high-temperature negative temperature coefficient ceramics based on scheelite or perovskite structures. The results suggested that the A2Sn2O7 (A = La, Nd, Sm, or Gd) ceramics could be potentially used for fabricating high-temperature NTC thermistors.