The microstructure and property evolution of LaYbZr2O7 thermal barrier coatings

The search for advanced thermal barrier coatings with high sintering resistance and low thermal conductivity has become increasingly urgent in the development of advanced gas turbines. In this study, we successfully fabricated a LaYbZr2O7 coating with exceptional thermal and mechanical properties. The microstructure and property evolution of the coating were comprehensively investigated after annealing at high temperatures. The as-sprayed LaYbZr2O7 coating exhibited a single pure fluorite phase, which subsequently transformed into a fluorite + pyrochlore phase after sintering at 1300 °C for 20 h. The phase transition resulted in a 0.4 % volume change, which occurred at high temperatures without causing any abrupt volume changes during heating and cooling processes. In comparison to YSZ coatings, the LaYbZr2O7 coating displayed an extremely low thermal conductivity both before and after heat treatment. Even after being exposed to 1200 °C for 200 h, its thermal conductivity remained at approximately 0.9 W·m−1·K−1, indicating excellent sintering resistance. The coating also exhibited sluggish grain growth, with an average grain size of <400 nm after exposure to high temperatures. The presence of superfine grains in the LaYbZr2O7 coating contributed to its high fracture toughness and hardness. These findings indicate that the LaYbZr2O7 coating is a promising advanced thermal barrier material for high-performance gas turbines.