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 （Tg） with the addition of ZnO is ascribed to the competition of two converse factors,i e,the Tg depression as one of the colligative properties for a solution,on the one hand,and the enhancement of Tg 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.