Unravelling the Electrical Degradation of Lacro3 at High Temperatures: Insights from Dfmd Simulations and Experimental Analyses

Abstract

Understanding the mechanisms underlying electrical degradation in perovskite-type LaCrO3 ceramics at high temperatures is crucial for prolonging its operational lifespan in applications such as sensors and solid oxide fuel cells. This study employs density functional based molecular dynamics to simulate the structural and total energy changes of a LaCrO3 supercell at elevated temperatures, revealing that the crystal structure becomes unstable above 600 °C. The emergence of heterovalent chromium oxides observed during high-temperature in situ X-ray diffraction tests conducted in an argon atmosphere, along with the disordering of the ceramic lattice revealed through high-resolution transmission electron microscopy after exposure to temperatures surpassing the critical threshold in an oxygen-free environment, supports this finding. Electrical measurements indicated substantial and progressive changes in the resistance of LaCrO3 ceramics at temperatures associated with structural instability. These results corroborate the mechanism that structural instability is the primary cause of electrical degradation at elevated temperatures, rather than the previously held notion of an oxidation mechanism. This degradation mechanism also holds promising applicability to other perovskite-type chromate systems, thus providing valuable insights and potential strategies for enhancing the long-term electrical stability of LaCrO3 ceramics and related chromate materials under high-temperature conditions.

Keywords: High-temperature electrical stability, Density functional based molecular dynamics, Electrical degradation, Chromate ceramics, Perovskite-type LaCrO3.