Rare Earth and Perovskite Composite Ceramics Applied for the Thermistor with Wide Temperature Range

Abstract

Different compositions (aY2O3+bCeO2)-0.4YCr0.5Mn0.5O3 (a+b=0.6) were prepared via a conventional solid-state reaction at 1200°C, and sintered under air atmosphere at 1600°C. XRD patterns analysis has revealed that for 0<a<0.6, the major phases present in the calcined bodies are Y2O3, CeO2 and orthorhombic perovskite YCr0.5Mn0.5O3 phase, respectively. SEM and EDAX observations confirm the obtaining of three-phased composite ceramics. The brighter regions are the Y2O3 and CeO2 phase, whereas the darker are perovskite phase. All the NTC thermistors prepared show a similar linear relationship between the ln of the resistance and the reciprocal of the absolute temperature, indicative of NTC characteristics. For 0≤a≤0.6, the plotting curves of resistance- temperature characteristic are none linear on the wide temperature range, exhibit two branches. The obtained B25/150 and B700/1000 constants of the thermistors are in the range 3600-4400K and 6700-12000K. The magnitude order of the resistivity at 25°C is of 106-107Ωcm and activation energies vary from 0.313 to 1.029 eV at low and high temperatures, respectively. These compounds, having good NTC characteristics in a wide range of temperatures, could be applied as potential candidates for NTC thermistors from ambient to 1100°C.