Ceramic compositions based on (aY2O3 + bCeO 2)-0.4YCr0.5Mn0.5O3 (a + b = 0.6) were prepared by conventional solid state reaction at 1200 °C, and sintered under air atmosphere at 1600 °C. For 0 ≤ a < 0.6, XRD patterns have shown that the major phases presented in the calcined powders are Y 2O3, CeO2 and orthorhombic perovskite YCr 0.5Mn0.5O3 phase, respectively. SEM and EDAX observations confirm the YCr0.5Mn0.5O3 phases mostly exist at the grain, whereas the Y2O3 and CeO 2 phases mainly exist at the grain boundaries. Complex impedance analysis shows that, for 0 < a ≤ 0.6, single semicircular arc whose shape does not show any change with temperature. Nevertheless, for a = 0, two overlapping semicircular arcs are observed at and above 300 °C. The grain boundary properties exhibit thermistor parameters with a negative temperature coefficient characteristic. The relaxation behavior and conduction for the grain boundary could be due to a space-charge relaxation mechanism and oxygen vacancies, respectively.
Chinese Acad Sci, Xinjiang Tech Inst Phys & Chem, Urumqi 830011, Peoples R China;Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China;Xinjiang Key Lab Elect Informat Mat & Devices, Urumqi 830011, Peoples R China
Zhang Bo,Zhao Qing,Chang Aimin,et al. Complex impedance analysis of (Y2O3 + CeO2)–YCr0.5Mn0.5O3 composite NTC ceramics[J]. Journal of Alloys and Compounds,2012,512(1):132-139.