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 at ambient conditions, using both Raman and Brillouin spectroscopies. The conventional nucleating agent, i.e., Zr⁴⁺ caused a more polymerized silicate network, amorphous phase separation before crystallization, and a significant drop in shear, Young's and bulk moduli, though Raman spectra have revealed that the partial substitution of Zr for Si occurred chiefly in the less polymerized Q² species. The compiled data of alkali silicate glasses M₂O–SiO₂ (M = Li, Na, K) showed that each glass displays different M₂O concentrations for getting minimum bulk modulus due to difference in field strength of cations, depolymerization 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 same constituents can be ascribed to different mechanisms for compression and shear deformation.