High-Entropy Chromate (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)CrO3 for High-Temperature NTC Thermistors

Abstract

This paper presents a novel rare earth-based chromate (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)CrO3 for high-temperature thermistor applications. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy tests reveal that the material is a high-entropy ceramic with a perovskite structure, exhibiting a dense microstructure with a relative density of 97.6%. Electrical analysis shows that (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)CrO3 exhibits high resistivity at high temperatures but with a material constant of 1,968 K, making it capable of meeting the resistance requirements for commercial thermistors over an ultrawide temperature range of 25 – 1,300 °C. AIMD simulations indicate the excellent structural stability of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)CrO3 even at 1,300 °C, suggesting promising high-temperature aging characteristics. Further aging tests demonstrate that its resistance only drifted by 4.57% after being subjected to 1,300 °C for 1,000 h. The above findings represent breakthroughs in terms of maximum operating temperature, applicable temperature range, aging performance and sintering densification for chromate-based high-temperature thermistor ceramics.

Keywords: High-entropy ceramics, Negative temperature coefficient, High-temperature NTC thermistors, Perovskite-structured chromate ceramics, Aging performance