No abstract

Aluminum nitride, a significant ceramic material used in electronic technological applications, was investigated by in situ synchrotron radiation X-ray diffraction in a diamond anvil cell at ambient temperature. The starting sample of AlN powder with a 1−2 μm average grain size was compressed to 36.9 GPa under the hydrostatic condition and 36.2 GPa under the nonhydrostatic condition, respectively. The phase transformation from hexagonal wurtzite to cubic rock salt (B4-to-B1) for the hydrostatic condition 20.5 and 20.4 GPa for the nonhydrostatic condition. We found that the phase transition was irreversible and that pure cubic phase AlN was obtained after pressure relief to reestablish ambient pressure. The experimental results reveal that the bulk modulus of hexagonal AlN is B 0 = 287.1 GPa at a fixed B 0 ′ = 4 under hydrostatic compression. For the recompressed pure cubic sample in the diamond anvil, the equation of state (EOS) of cubic AlN is B 0 = 357.0 GPa when fit from ambient pressure to 39.5 GPa. The high pressure leads to the changes of atomic positions, bond distances, and bond angles, which were obtained from analysis using the refined GSAS package software, and explains the phase transition mechanism of hexagonal to cubic structure. In addition, the hexagonal AlN starts to exhibit a plastic deformation at approximately 8.5 GPa under nonhydrostatic compression, which is very close that of TiN by comparison.

Zirconia-yttria films containing 8.0wt% Y2O3 were prepared on a Si substrate with r.f. magnetron sputtering deposition followed by 170 KeV Ar+ ion irradiation at room temperature. The characterization of these zirconia-yttria films with different ion bombarding doses has been studied by XRD, XPS and AES. It was found that all the films consisted of three portions, the amorphous films deposited with r.f. magnetron-sputtering were partially crystallized and nontransformable tetragonal (T') phase was detected after Ar+ ion bombardment of a dose of 1×1016 ion/cm2, and the oxidized states of Zr3d, Y3d and Ols peaks of XPS were observed under the conditions of argon ion bombardment of different doses.

No abstract