Enhanced Temperature Range and Stability in LaAlO3 NTC ceramics through Ce-Nb Codoping

Abstract

Negative temperature coefficient (NTC) thermistors have garnered increased attention due to their high sensitivity, low thermal inertia, and cost-effectiveness. However, their practical application is significantly constrained by a limited temperature range and poor stability. In this study, a series of Ce-Nb codoped LaAlO₃ ceramics were synthesized using the traditional solid-state reaction method, and their unique electrical properties as NTC thermistors were examined. XRD analysis reveals that Ce-Nb codoping induces lattice distortion in the LaAlO₃ ceramics. HAADF-STEM shows that Ce replaces La at A-sites, while Nb substitutes for Al at B-sites. XPS indicates that the substitution of Ce⁴⁺ for La³⁺ and Nb⁵⁺ for Al³⁺ facilitates the formation of oxygen vacancies and enhances the number of free carriers. Electrical resistance and UV measurements demonstrate that increasing the Ce and Nb doping levels improves carrier mobility and reduces the band gap of LaAlO₃. These modifications significantly enhance the electrical performance and extend the temperature range to 298 K –1773 K when the Ce doping level is 0.2 and the Nb doping level is 0.1. Additionally, aging tests indicate that Ce-Nb co-doping reduces the aging drift of LaAlO₃ to 0.38% after 500 h of aging at 1273 K. This novel Ce-Nb codoped LaAlO₃ ceramic, with its broad temperature range and superior stability, shows significant potential for application in NTC thermistors.