A novel LaAl1-xNbxO3 NTC ceramic with excellent stability for high-temperature thermistor

A series of LaAl 1- x Nb x O 3 (0 ≤  x  ≤ 0.100) samples were synthesized via the solid phase method. Characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) confirmed the formation of a solid solution in LaAl 1- x Nb x O 3 (0 ≤  x  ≤ 0.100) materials without the emergence of additional phases following Nb doping. Transmission electron microscopy (TEM) revealed distinct lattice fringes with a d value of 0.274 nm, corresponding to the (110) plane of LaAlO 3 (PDF #82–0478). The introduction of Nb dopant caused distortions in the cell parameters of LaAlO 3 due to ionic radius size effects, changes in Nb valence, fluctuations in oxygen vacancy concentration and Coulomb forces. Specifically, the lattice exhibited a shrinkage for 0 ≤ x  ≤ 0.025, expansion for 0.025 < x  ≤ 0.075, and subsequent shrinkage for 0.075 < x  ≤ 0.100. Resistance measurements indicated that LaAl 1- x Nb x O 3 (0 ≤  x  ≤ 0.100) materials exhibited favorable negative temperature coefficient (NTC) characteristics in the temperature range of 600 °C–1400 °C. Hall measurements revealed that the materials functioned as P-type semiconductors with hole carriers, and Nb doping enhanced carrier concentration. Aging tests demonstrated that the aging drift rate of LaAl 0.9 Nb 0.1 O 3 could be as low as 0.906% after aging it at 1000 °C for 500 h, a crucial parameter for practical applications of LaAl 1- x Nb x O 3 (0 ≤  x  ≤ 0.100) materials in high-temperature NTC applications.