Synchrotron-based x-ray-diffraction study of the intermediate-high-pressure phase in the alloy In_0.25 Sn_0.75

In_0.25Sn_0.75 alloy stabilized in the primitive hexagonal phase at ambient conditions is studied in a diamond anvil cell at high pressures with angle-dispersive x-ray diffraction using the synchrotron radiation at ELETTRA. The ambient primitive hexagonal phase was found to undergo a reversible transformation to a mixture of body-centered-tetragonal and hexagonal-close-packed phases above 11.6 GPa and not to the Cmca structure assigned in Si and Ge. The occurrence of the bct phase shows similarity to the high-pressure behavior of Sn. A transformation mechanism from the ph to hcp phase via the bct structure is also described.