Elastic properties of silicate melts up to 2350 K from Brillouin scattering

Abstract

Compressional wave velocities ( V p ) have been determined up to 2350 K on CaSiO 3 , MgSiO 3 , CaMgSi 2 O 6 , CaAl 2 Si 2 O 8 and Ca 3 Al 2 Si 3 O 12 glasses and melts from Brillouin‐scattering experiments made with a 180° backscattering geometry. At the glass transition, the decrease of V p with increasing temperatures becomes much stronger and the width of the Brillouin lines begins to increase markedly. At the highest temperatures investigated, V p is similar to the relaxed values determined in acoustic measurements for several of these melts. This indicates that the configurational degrees of freedom of these liquids have become accessible within the very short timescale of Brillouin scattering experiments: equilibrium compressibilities of silicate melts can thus be determined with this technique. Our measurements also suggest that the shear modulus at infinite frequency of silicate melts could vary with either temperature or composition more strongly than assumed currently.