Elasticity and lattice vibrational properties of transparent polycrystalline yttrium-aluminium garnet: Experiments and pair potential calculations

摘要

Brillouin light scattering, Raman light scattering and visible-infrared reflectometry techniques have been used to investigate, respectively, the elastic properties, the phonons and the optical properties of bulk textured polycrystalline yttrium-aluminum garnet doped with 2 at percent neodymium obtained by the sintering of commercial oxides. From the analysis of the observed bulk longitudinal and transverse acoustic modes with the knowledge of the refractive index 1.81 inferred from the visible reflectometry, the two independent effective elastic constants of the isotropic polycrystal C_(11) velence 362 GPa and (C_(11) - C_(12))/2 velence 121 GPa are determined leading to the value of the bulk modulus B velence (C_(11)+ 2C_(12))/3 velence 200 GPa. The ratio epsilon_0/epsilon_(infinity) velence 3.1 and the optic permittivity epsilon_(infinity) velence 3.46 are derived from the infrared reflectivity data. Pair potential calculations of the three single crystal elastic constants c_(11) velence 340, c_(12) velence 127 and c_(44) velence 112 GPa, of the bulk modulus B velence (c_(11) +2c_(12))/3 velence 198 GPa, of the zone-center (GAMMA) phonons and of the permittivity function provide good comparison with our experimental results.