Mixed Alkali-zinc Effects on Thermo-mechanical Properties in Borosilicate Glasses

A series of mixed alkali-zinc borosilicate glasses with various r values (r = molar ratio of [ZnO] / ([R₂O]+[ZnO])) from 0.00 to 1.00 were fabricated to probe the mixed alkali-zinc effects on thermo-mechanical properties. The nonlinear evolution of glass transition temperature (T_g) with the addition of ZnO is ascribed to the competition of two converse factors, i e, the T_g depression as one of the colligative properties for a solution, on the one hand, and the enhancement of T_g due to the higher field strength of zinc cations compared to that of alkali ions. However, the nonlinear evolution of elastic moduli and coefficients of thermal expansion with r is attributed to the variance of intermediate-range clusters, which is confirmed by infrared and Raman scattering spectra. These findings are very helpful in tailoring the performance of borosilicate glasses.