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

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% 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 C11 = 362 GPa and (C11 − C12)/2 = 121 GPa are determined leading to the value of the bulk modulus B = (C11 + 2C12)/3 = 200 GPa. The ratio ɛ0/ɛ∞ = 3.1 and the optic permittivity ɛ∞ = 3.46 are derived from the infrared reflectivity data. Pair potential calculations of the three single crystal elastic constants c11 = 340, c12 = 127 and c44 = 112 GPa, of the bulk modulus B = (c11 + 2c12)/3 = 198 GPa, of the zone-center (Γ) phonons and of the permittivity function provide good comparison with our experimental results.