Equation of state of gallium oxide to 70 GPa: Comparison of quasihydrostatic and nonhydrostatic compression
- UNLV
Synchrotron x-ray diffraction and diamond-anvil cell techniques were used to characterize pressure induced structural modifications in gallium oxide. Gallium oxide was studied on compression up to 70 GPa and on the following decompression. The effect of the pressure-transmitting medium on the structural transformations was investigated in two sets of compression and decompression runs, one with nitrogen as a quasihydrostatic pressure-transmitting medium and the other in nonhydrostatic pressure conditions. The x-ray diffraction data showed gradual phase transition from a low-density, monoclinic {beta}-Ga{sub 2}O{sub 3} to a high-density, rhombohedral {alpha}-Ga{sub 2}O{sub 3}. With the use of nitrogen as a pressure transmitting medium, the {beta}- to {alpha}-Ga{sub 2}O{sub 3} transition begins at about 6.5-7 GPa and extends up to {approx}40 GPa, confirming recent theoretical calculations. This pressure-driven transition is irreversible and the material decompressed from 70 GPa to ambient conditions was composed, in both sets of experimental runs, of {alpha}-Ga{sub 2}O{sub 3} only. A Birch-Murnaghan fit of the unit cell volume as a function of pressure yielded a zero pressure bulk modulus K{sub 0}=199(6) GPa, and its pressure derivative K{sub 0}'=3.1(4) for the {beta}-Ga{sub 2}O{sub 3} phase, and K{sub 0}=220(9) GPa and K{sub 0}'=5.9(6) for the {alpha}-Ga{sub 2}O{sub 3} phase for the experiments performed in quasihydrostatic compression conditions. When for the same experiment K{sub 0}' is held at 4, then the bulk modulus values are 184(3) and 252(14) GPa for {beta}-Ga{sub 2}O{sub 3} and the {alpha}-Ga{sub 2}O{sub 3}, respectively. We compare the results of this work with our previous studies on the high-pressure behavior of nanocrystalline gallium oxide.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1006573
- Journal Information:
- Phys. Rev. B, Vol. 77, Issue 2008; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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