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Article Dans Une Revue Journal of Applied Physics Année : 2021

Influence of elastic anisotropy on measured sound velocities and elastic moduli of polycrystalline cubic solids

Résumé

Cubic solids such as NaCl, crystalline argon, or H 2 O-ice VII exhibit significant elastic anisotropy strongly increasing upon compression. As earlier recognized for solid argon and H 2 O-ice (both exhibiting Zener ratio A>1), longitudinal sound velocities of their polycrystals, V Lav , measured using Brillouin light scattering (BLS) or pulse-echo ultrasonics are much closer to V L111 than to V L100 , the V L-extremes in any cubic single crystal. Here, we experimentally confirm, using the technique of time-domain Brillouin scattering, the same tendency for NaCl exhibiting the opposite anisotropy type, A<1. To understand this tendency, we modelled orientational distribution and the frequency of occurrence of V L values in texture-free polycrystalline samples of NaCl and solid argon. We found a remarkable and predictable asymmetry of the V L distributions with maxima at V L110 which is always much closer to V L111. This asymmetry persists in BLS peaks but can be obscured in experiments. In the case of solid argon at 49 GPa, the asymmetry can lead to a moderate deviation of experimental V Lav from V LH (obtained from elastic-stiffness constants C ij applying the Hill approximation) by ~7%. The latter can cause, however, a significant overestimation of the aggregate shear modulus by δG/G~50% or of the bulk modulus by δB/B~20% if just one BLS peak of longitudinal modes is detectable. A similar analysis, performed for transverse sound velocities, V T and V Tav , has shown that, by use of a BLS spectrum showing peaks of both longitudinal and transverse modes, overestimation of B is similarly high but that of G is much less dramatic.
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Dates et versions

hal-03411770 , version 1 (02-11-2021)

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Feng Xu, Philippe Djemia, Laurent Belliard, Haijun Huang, Bernard Perrin, et al.. Influence of elastic anisotropy on measured sound velocities and elastic moduli of polycrystalline cubic solids. Journal of Applied Physics, 2021, 130 (3), pp.035903. ⟨10.1063/5.0053372⟩. ⟨hal-03411770⟩
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