Brillouin spectra of mixed alkali glasses: xCs2O(1−x)Na2O5SiO2

The Brillouin spectra of a series of mixed alkali glasses, of the composition _xCs₂O(1?x)Na₂O5SiO₂, have been measured and analyzed. Significant nonlinearities are found for the variation of the isothermal compressibility [K_T,0(T_f)] and Landau-Placzeck ratio, with a minimum observed in each as a function of x, while the longitudinal and transverse sound velocities and related elastic constants, C₁₁, C₄₄ and Young's modulus, E, vary monotonically (nearly linearly) with x. The results are interpreted in connection with related ultrasonic data and the effect of varying composition on the mechanical properties of mixed alkali glasses.