Improving oxidation resistance of ZrB2-based ceramics by LaF3 doping via oxidation-induced self-healing mechanism

Abstract ZrB2-based ceramics are important materials for a variety of applications. However, their low oxidation resistance above 1000 °C limits their high-temperature applications. Herein, we report the utilization of LaF3 as a unique oxidation retardant to significantly improve the oxidation resistance of ZrB2-10 vol%LaF3 ceramics in the temperature range of 1000-1400 °C. Moreover, we present the densification of the oxide layer via oxidation-induced self-healing mechanism of ZrB2-LaF3 ceramics for the first time. The incorporation of LaF3 into ZrB2 matrix was achieved by using spark plasma sintering at 1800 °C. Furthermore, the oxidation behavior of pure ZrB2 and ZrB2-10 vol%LaF3 ceramics was systematically investigated by analyzing the thicknesses of oxide layers and the weight gains. Both the thicknesses and weight gain were significantly reduced after adding 10 vol. % LaF3, which can be mainly attributed to the synergistic influence of pore filling and healing by LaB3O6/LaBO3 phases and corresponding volumetric expansions.