A novel negative temperature coefficient material based on lanthanum zirconate ceramics was proposed for high-temperature applications. This material was synthesized through a solid-state reaction by sintering at 1923 K for 10 h in air. The X-ray diffraction and scanning electron microscopy results confirmed that La 2 Zr 2 O 7 ceramics exhibited a pyrochlore phase with a relative density of 98.2 %. The resistance–temperature characteristics of the material revealed that La 2 Zr 2 O 7 ceramics exhibited an NTC feature within the broad temperature range of 973–1773 K in addition to maintaining high thermal constant B , and resistivity to ensure good sensitivity at high temperatures. These properties, along with high ceiling temperature, unique oxygen insensitivity, and excellent ageing coefficient of <0.7 % at 1773 K, render La 2 Zr 2 O 7 ceramics a promising candidate as thermistor materials with high-temperature NTC.
High density negative temperature coefficient (NTC) thermistor ceramics Bi 0.2-x Ce x Sr 0.5 La 0.3 TiO 3 (0 < x < 0.05) (BCSLTO) were synthesized by the Pechini method. This work is the first to characterization analysis the excellent NTC characteristics of BCSLTO ceramics at high temperatures. BCSLTO NTC thermistor ceramics have wide operating temperature is 300 °C-1000 °C, and mild sintering conditions with the conventional sintering at 1250 °C. The important electrical performance parameters of BCSLTO ceramics are as follows: the resistivities at 300 °C, 700 °C, and 1000 °C are 3.26 × 10 9 –8.99 × 10 7 Ω cm, 2.21 × 10 5 –1.05 × 10 5 Ω cm, and 1.18 × 10 3 –1.13 × 10 3 Ω cm, respectively; the thermal constant B 300/700 is 13385.9–9408.8 K; the activity energy Ea 300/700 is 1.15–0.81 eV. The resistivity and the thermal constant B can be widely control by doping Ce. In addition, the resistivity drift improves as the Ce doping content increases (below 5%). The new high-temperature Bi 0.2-x Ce x Sr 0.5 La 0.3 TiO 3 ceramic materials with mild sintering conditions, wide operating temperature and high-temperature stability can be used as potential candidates for high temperatures and harsh environments.
The perovskite CaMn x Zr (1- x ) O 3 ( x = 0, 0.05, 0.10, 0.15) (CMZO) NTC (Negative Thermal Coefficient) thermo-sensitive ceramic were prepared by the solid phase method that can be used as high temperature thermistor materials in the range of 200–1200 °C.The XRD pattern showed that CMZO is a finite solid solution and that a second phase, CaMnO 3 , will be formed after exceeding the solid solution limit (i.e., at x = 0.1). The thermal constant B value was found to decrease from 19521 K to 9217–9535 K, with a corresponding decrease in activation energy , E a , from 1.69 eV to 0.82 eV. The Nyquist plot indicates that the grain boundary resistance determines the overall complex impedance. Moreover, the aging drift rate (ΔR/R 0 ) was found to be lower than 4.3%, which is an indication of an excellent high temperature stability of the CMZO ceramic material.
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