Composition dependent structure and elasticity of lithium silicate glasses : Effect of ZrO2 additive and the combination of alkali silicate glasses

The elasticity and structure of lithium silicate glasses Li2O.3SiO2, Li2O.2SiO2, and Li2O.2SiO2.0.135ZrO2 were studied under ambient conditions, using both Raman and Brillouin spectroscopy. The conventional nucleating agent, i.e., Zr4+ caused a more polymerised silicate network, amorphous phase separation before crystallisation, and a significant drop in shear, Young's and bulk moduli, though Raman spectra showed that the partial substitution of Zr for Si occurred chiefly in the less polymerised Q2 species. The compiled data of alkali silicate glasses M2O-SiO2 (M = Li, Na, K) showed that each glass displays different M2O concentrations to obtain minimum bulk modulus due to difference in field strength of cations, depolymerisation of silicate network, and coordination number of cations. The specific M2O concentrations for such minima increase with increasing cation size. Different composition dependences of elastic moduli for the glasses having the same constituents can be ascribed to different mechanisms for compression and shear deformation. 52 refs.