Stability of Zirconium Carbide under High Pressure and High Temperature

As a prototype refractory and hard transition-metal carbide, the stability of zirconium carbide (ZrC) under extreme conditions is critical for its applications. Despite the extensive theoretical studies, few experimental results are available until now. In this work, we carried out a comprehensive experimental study of ZrC in a large unexplored pressure–temperature region (up to ∼150 GPa and ∼2000 K) by combining in situ high-pressure and high-temperature synchrotron radiation X-ray diffraction with various ex situ characterization techniques. Our results demonstrate that ZrC (B1 phase) remains stable up to ∼154 GPa at room temperature or at ∼40 GPa up to 2000 K, rather than undergoing the predicted B1-to-B2 phase transition. However, under high pressure and temperature, ZrC is extremely active when water is present. It would react with even trace amount of absorbed water to form ZrO2 and CH4. Our results clarify the structural and chemical stability of ZrC at extreme conditions, which would guide the applications of ZrC and provide new experimental constraint for theoretical calculations.