High-pressure behavior of $β-Ga2O3$ nanocrystals Available to Purchase

Freestanding nanocrystalline $β-Ga2O3$ particles with an average grain size of 14 nm prepared by chemical method was investigated by angle-dispersive synchrotron x-ray diffraction in diamond-anvil cell up to 64.9 GPa at ambient temperature. The evolution of x-ray diffraction patterns indicated that nanocrystalline monoclinic $β-Ga2O3$ underwent a phase transition to rhombohedral $α-Ga2O3$⁠. It was found that $β-$ to $α-Ga2O3$ transition began at about 13.6–16.4 GPa, and extended up to 39.2 GPa. At the highest pressure used, only $α-Ga2O3$ was present, which remained after pressure release. A Birch–Murnaghan fit to the $P-V$ data yielded a zero-pressure bulk modulus at fixed $B0′=4$⁠: $B0=228(9)GPa$ and $B0=333(19)GPa$ for $β-Ga2O3$ and $α-Ga2O3$ phases, respectively. We compared our results with bulk $β-Ga2O3$⁠, and concluded that the phase-transition pressure and bulk modulus of nanocrystalline $β-Ga2O3$ are higher than those of bulk counterpart.