T-P phase diagram of the Mo-H system revisited

The T-P phase diagram of the Mo-H system studied earlier at hydrogen pressures up to 5.3 GPa and temperatures up to 1200 °C by in-situ X-ray diffraction [Y. Fukai et al. Mater. Trans. 44 (2003) 1359] is re-examined at P ≤ 6 GPa and T ≤ 800 °C using a quenching technique. The formation of the high-temperature fcc MoH hydride at T > 480-570 °C is not confirmed. Instead, the stability region of the low-temperature hcp MoH1.1 hydride is found to grow with pressure. The temperature of its boundary with the region of diluted Mo-H solutions rises with pressure and reaches 800 °C at P ≈ 5.5 GPa.