Brillouin scattering in aluminosilicate glasses and melts up to 2550 K. Temperature and composition effects

Abstract

Hypersonic sound velocities have been measured by Brillouin scattering for glasses and liquids of the system CaO-MgO-Al₂O₃-SiO₂ (CMAS). Transverse wave velocities are reported for ten samples from 293 up to temperatures ranging from 1000 to 1600 K, depending on composition, and longitudinal velocities for six samples from 293 to the interval 1890–2360 K. For the 13 CMAS compositions, the temperature dependences of acoustic velocities are constant within three temperature intervals: (i) from 293 K to the standard glass transition temperature T_g, (ii) from T_g, to the temperature T_rx of the onset of structural relaxation at the timescale of Brillouin scattering where transverse waves disappear, (iii) and finally above T_rx where only longitudinal waves thus remain observed. The implications of these results for structural relaxation, shear-wave propagation and shear modulus are then discussed.