Structural stability of ultra-high temperature refractory material MoSi₂ and Mo₅Si₃ under high pressure

In-situ angle dispersive x-ray diffraction (ADXRD) with synchrotron radiation source is performed on an ultra-high temperature refractory of MoSi₂ and Mo₅Si₃ by using a diamond anvil cell (DAC) at room temperature. While the pressure-induced volume reduction is almost constant, the value of the bulk modulus increases with the decrease of molybdenum content in the system. According to the Brich-Murnaghan equation, the bulk modulus 222.1 (2.1) GPa with its pressure derivative 4 of MoSi₂, and the bulk modulus 308.4 (7.6) GPa with its pressure derivative 0.7 (0.1) of Mo₅Si₃ are obtained. The experimental data show that MoSi₂ has distinct anisotropic behavior, Mo₅Si₃ is less anisotropic than MoSi₂. The result shows that MoSi₂ and Mo₅Si₃ have the structural stabilities under high pressure. When the pressure reaches up to 41.1 GPa, they can still maintain their body-cantered tetragonal structures.