La2O3-doped 0.6Y2O3–0.4YCr0.5Mn0.5O3 composite NTC ceramics for wide range of temperature sensing

• The effect of the La2O3 dopant on the electrical properties is investigated.
• There is a solubility limit of the substitution of La3+ for Y3+ for calcined powders.
• The La2O3-doped ceramics show good NTC characteristics over a wide temperature range.

Ceramic compositions based on 0.6Y2O3–0.4YCr0.5Mn0.5O3 doped with La2O3 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 LaCr0.5Mn0.5O3 phase when the amount of La2O3 increases to 5.0 wt% in the calcined powders. Major phases presented in the sintered ceramics are Y2O3 phase and orthorhombic perovskite phase isomorphic to YCrO3. The obtained ρ25, B25/150 and B700/1000 constants of the La2O3-doped NTC thermistors are in the range of 105–106 Ω cm, 3600–3800 K and 6000–6600 K, respectively. The electrical conductivity in these compounds may be due to the presence of Cr3+, Cr4+, Mn3+ and Mn4+ 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.