Low-temperature behavior of potassium and sodium silicate glasses

Abstract

In a study of the low-temperature anomalies which appear in disordered solids we have measured the specific heat, thermal conductivity, thermal expansion, and dielectric dispersion for a carefully prepared series of (${\mathrm{SiO}}_2$ ${)}_{1\mathrm{-}\mathrm{x}}$(${\mathrm{K}}_2$O${)}_{\mathrm{x}}$ and (${\mathrm{SiO}}_2$ ${)}_{1\mathrm{-}\mathrm{x}}$(${\mathrm{Na}}_2$O${)}_{\mathrm{x}}$ glasses. Each sample had a known glass transition temperature $T_g$, mass density, phonon velocities, covalency, and density and concentration fluctuations. The only significant correlation occurred between the phonon mean free path and the glass-transition temperature. No explicit support was found for any model developed to explain the specific heat and/or thermal conductivity of glasses.