Enhanced temperature range and stability in LaAlO3 NTC ceramics through Ce-Nb codoping

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. •Ce-Nb codoped LaAlO3 ceramics significantly increase the electricity content and widen the temperature range to 298–1773 K.•The conductivity mechanism is analyzed from the oxygen vacancies, energy band and a small polaron hopping conduction model.•The aging results illustrate that Ce-Nb codoping reduces the aging drift of LaAlO3 to 0.38%.•This novel Ce-Nb codoped LaAlO3 ceramic has significant application prospects for NTC thermistors.