La2O3-doped 0.6Y(2)O(3)-0.4YCr(0.5)Mn(0.5)O(3) composite NTC ceramics for wide range of temperature sensing

Abstract Ceramic compositions based on 0.6Y 2 O 3 –0.4YCr 0.5 Mn 0.5 O 3 doped with La 2 O 3 were prepared by solid state reaction at different calcining temperatures, and sintered at 1550 and 1600 °C. XRD patterns have shown that there exists a LaCr 0.5 Mn 0.5 O 3 phase when the amount of La 2 O 3 increases to 5.0 wt% in the calcined powders. Major phases presented in the sintered ceramics are Y 2 O 3 phase and orthorhombic perovskite phase isomorphic to YCrO 3 . The obtained ρ 25 , B 25/150 and B 700/1000 constants of the La 2 O 3 -doped NTC thermistors are in the range of 10 5 –10 6  Ω cm, 3600–3800 K and 6000–6600 K, respectively. The electrical conductivity in these compounds may be due to the presence of Cr 3+ , Cr 4+ , Mn 3+ and Mn 4+ on octahedral sites. The resistance almost does not change when the aging time is from 600 to 1000 h. Such ceramics could be used as potential candidates for NTC thermistors in a wide temperature range from ambient to 1100 °C.