Modulation of the microstructure and electrical properties of LaAlO3 ceramics induced by doping with rare earth elements (Eu, Gd, Ho, and Tm)

Abstract

This study synthesized La_0.9X_0.1AlO₃ (X = Eu, Gd, Ho, Tm) and LaAlO₃ ceramics by a solid-state method. The characterization of the ceramics revealed that the high degree of lattice distortion induced by variations in the size, mass, and electronegativity of rare-earth elements enhances high-temperature stability, leading to aging drift rates between 0.4% and 2.3% after 500 h at 1000 °C. Furthermore, the emergence of intrinsic defects and dislocations alters the charge conduction mode in LaAlO₃, resulting in significant linearity at temperatures above 1000 K. This study further elucidates the transition in the charge conduction mechanism from thermally activated conduction to hopping conduction, which is driven primarily by oxygen vacancies and dislocations. DFT calculations support these findings, demonstrating a reduction in the band gap and increased carrier concentration. This work paves the way for the development of advanced NTC thermistors for reliable temperature monitoring in challenging environments.