Influence of dispersion method of LaF3 in ZrB2-based ceramics on high-temperature oxidation resistance

The high-temperature applications of zirconium diboride (ZrB 2 ) ceramics are hindered due to their easy initial oxidation at temperature around 700 °C. Although mixing and coating methods have been introduced to enhance the oxidation resistance of ZrB 2 -based ceramics, their thorough comparative analysis still demands a more systematic exploration. Herein, spark plasma sintered ZrB 2 @20 vol% LaF 3 and ZrB 2 +20 vol% LaF 3 ceramics prepared by coating and mixing powders, respectively, were used to study the influence of dispersion method of LaF 3 on their oxidation resistance. After oxidation at 1000 °C for 4 h, a thin oxide layer (~25 μm) and low weight gain (9%) confirmed the superior oxidation resistance of ZrB 2 +20 vol% LaF 3 over ZrB 2 @20 vol% LaF 3 , which could be attributed to the formation of a dense surface layer due to the self-healing mechanism. In turn, the poor oxidation resistance of ZrB 2 @20 vol% LaF 3 was caused by the “anchoring” of LaF 3 cladding layer and locally-coated ZrB 2 particles, which led to the in situ reactions and formation of a porous oxide scale (~400 μm). Finally, the discrepant oxidation resistance mechanisms of ZrB 2 –LaF 3 ceramics obtained by different dispersion methods of LaF 3 were proposed.