Brillouin scattering of V2O5 and Sn-intercalated V2O5

The Brillouin scattering spectra of alpha-V2O5 and Sn-intercalated V2O5 (Sn0.07V2O5) were measured for sound propagation directions at and near the [001] direction, which is normal to the van der Waals gaps in this layered material. Anisotropic sound velocities and stiffness tensor elements c(ij) were determined from the Brillouin frequency shifts. Measurements for propagation in the [001] direction in pure V2O5 yielded c(33 )= 42.20 +/- 0.38 GPa, c(44) = 23.55 +/- 0.27 GPa, and c(55) = 25.65 +/- 0.27 GPa showing substantial disagreement with some published theoretical calculations. High longitudinal stiffness values similar to 230 GPa in the [100] and [010] directions correspond to remarkably high longitudinal sound velocities of 8290 m/s, demonstrating strong anisotropy associated with the layered structure. Sn-0.07 V2O5 was found to have stiffnesses of c(33) = 43.72 +/- 0.23 GPa, C-44 = 22.91 +/- 0.20 GPa, and c(55) = 26.54 +/- 0.22 GPa, indicating that some deformation modes are slightly stiffened while others may be unaffected or even softened by the intercalant.