Low-temperature elastic constants of monocrystal corundum (α-Al₂O₃)

Abstract

A complete set of low-temperature second-order elastic constants of corundum (-AlO) was studied by resonant ultrasound spectroscopy. At ambient temperature, the obtained show excellent agreement with those reported by Gladden et al. Our exhibit monotonic elastic softening upon cooling, but stay positive over the entire temperature range considered. From a lattice-dynamics analysis, the softening can be attributed to an internal displacement that has two-dimensional symmetry. The acoustic Debye temperature and Grüneisen parameter are calculated to be K and , respectively. The Einstein temperatures, estimated from curves, are relatively small compared to indicating that low-frequency modes are dominant in the zone-centred mode lattice vibrations. Also is essentially temperature independent.

Keywords:

• corundum (α-Al₂O₃)
• low-temperature elastic constants
• Debye temperature
• resonant ultrasound spectroscopy
• lattice dynamics

Acknowledgments

The authors acknowledge Mr Y. Kishida for help in performing the experiments.