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Pressure-Induced Structural Phase Transformation and Yield Strength of AlN
journal contribution
posted on 2019-11-11, 12:33 authored by Hong Yu, Fang Peng, Hao Liang, Shixue Guan, Lijie Tan, Zhengbi Xiong, Xiaojun Xiang, Qingze Li, Li Lei, Duanwei HeAluminum
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 B0 = 287.1 GPa at
a fixed B0′ = 4 under hydrostatic
compression. For the recompressed pure cubic sample in the diamond
anvil, the equation of state (EOS) of cubic AlN is B0 = 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.