Effect of Ni‐Doped Induced Stacking Faults on the NTC Properties and Aging Stability of La _0.9 Nd _0.1 Al _1‐x Ni _x O ₃ Ceramics

Owing to its wide bandgap, LaAlO₃ has garnered extensive attention in the field of high-temperature negative temperature coefficient (NTC) thermistors. However, its poor thermal stability and excessively high B value limit the working temperature range. In this work, introducing O 2p and Ni 3d hybrid energy levels into the bandgap is proposed via Ni doping and inducing stacking faults in the crystal structure to narrow the bandgap and enhance aging performance. Density functional theory (DFT) calculations indicate that the hybrid energy levels within the bandgap reduce the energy required for electron transitions. As a result, LaAlO₃ exhibits a lower B value of 1565 K, with the lower limit of the temperature range extending to -100 °C. Structural analysis reveals that as the Ni content increases, the crystal structure transitions from the R-3c phase to the Pm-3m phase at room temperature, with stacking faults predominantly observed in Ni-enriched regions. The introduction of these stacking faults causes oxygen vacancies to shift from a disordered to an ordered arrangement, forming a stable percolation network. This network inhibits the random diffusion of oxygen vacancies, thereby reducing aging instability from 33% to 4%. This work demonstrates the feasibility of improving NTC performance through stacking fault engineering.