<p>The Debye temperature is a parameter that reflects lattice vibrations and provides important insights into physics, chemistry, and related fields. In Mössbauer spectroscopy, it is reflected in the recoilless fraction. In ¹⁹⁷Au Mössbauer spectroscopy, the energy of γ-rays is higher than that of ⁵⁷Fe, making differences and changes in the recoilless fraction more pronounced. In this study, we investigated the properties of Au particles and the effects of the support in Au-supported catalysts using the recoilless fraction, which reflects the Debye temperature. For the Au/TiO₂ catalysts, the 10wt%Au sample exhibited a Debye temperature close to that of the bulk gold. In contrast, the 2.5wt%Au sample, in which the Au particles were finer, showed a lower Debye temperature than the bulk value. This indicates that, in the Au/TiO₂ 2.5wt%Au sample, the reduction in particle size resulted in lattice softening. Lattice vibrations influence the adsorption and migration of atoms on the surface; therefore, this difference may have affected the catalytic activity. The Au/SiO₂ 2wt%Au sample exhibited a Debye temperature close to that of bulk gold.</p>