High-pressure behavior of β-Ga2O3 nanocrystals
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.