Electrical properties and aging mechanism of Y2O3–MCr0.5Mn0.5O3 (M = Sm, Gd) composite NTC ceramics

Abstract

We report the structure and negative temperature coefficient (NTC) electrical properties of Y2O3–MCr0.5Mn0.5O3 (M = Sm, Gd) composite thermistor ceramics. The high-temperature aging mechanism has been revealed by using defect chemistry theory in combination with X-ray photoelectron spectroscopy analysis. The composite ceramics consist of Y2O3 and perovskite phase. All the NTC thermistors show a linear relationship between the natural logarithm of the resistivity and the reciprocal of the absolute temperature, indicative of the small-polaron hopping conductivity. The resistivity increases with the increase of Y2O3 content for Y2O3–SmCr0.5Mn0.5O3 and Y2O3–GdCr0.5Mn0.5O3 composite ceramics, respectively. The resistivity at 300 °C is in the range 102–104 Ω cm together with a B 300/800 from 4163 to 5614 K. The resistance decreases after high-temperature aging, suggesting that both aging atmosphere and the concentration of oxygen vacancies play a significant role in the change of electrical conductivity.