The Voigt-Reuss-Hill (VRH) Approximation and the Elastic Moduli of Polycrystalline ZnO, TiO2 (Rutile), and α-Al2O3

The Voigt-Reuss-Hill (VRH) approximation, a useful scheme by which one calculates isotropic polycrystalline elastic moduli in terms of the anisotropic single-crystal elastic constants, is shown to be accurately applicable for ZnO, TiO2 (rutile), and α-Al2O3, which are the simplest examples of oxide materials with the hexagonal, tetragonal, and trigonal symmetries, respectively. An experimental proof is established by measuring isotropic elastic moduli on dense-formed polycrystalline specimens. The recommended values of the polycrystalline isotropic elastic moduli of these oxides at room temperature are as follows: for ZnO, G=4.56(±0.04) and E=12.35(±0.09); for TiO2, G=11.15(±0.09) and E=28.42(±0.14); and for α-Al2O3, G=16.35(±0.12) and E=40.39(±0.31), where G and E are the isotropic shear and Young's moduli, respectively, and they are in units of 1011 dyn/cm2.

Hali tarjima qilinmagan