Mixed alkali effect on Vickers hardness and cracking

Mechanical properties of soda–lime–silica glasses with varying alkaline earth contents

“…In addition the literature indicates that alkaline earths also play an important role in controlling the mechanical properties. Thus the results of Deriano et al 7 and Hand and Tadjiev 2 indicate that increased fracture toughness values may be obtained by increasing the MgO content, while reducing the CaO content at constant SiO2 and Na2O concentrations. The ionic radius and coordination number of Mg are smaller than those of Ca and thus substitution of MgO for CaO gives higher molar volumes which it is suggested may explain the increase in fracture toughness 4 .…”

“…Bulk glass production is based on a limited range of soda-lime-silica (SLS) compositions with 90% of all glass manufactured globally having this type of composition 3 , albeit containing a range of other minor components. Even within a restricted compositional range some variation of mechanical properties with composition is to be expected and a number of authors have reported studies looking at such effects 1,2,4,5,6,7 . Most of the reported work is largely empirical, although Makashima and Mackenzie suggested an essentially linear model for calculating how the elastic moduli of a range of silicate and borate glasses vary with composition in the 1970s 8,9 .…”

“…Other work has given indications of non-linear variations in mechanical properties when one alkali is exchanged for another 4,5,7 with reduced ionic mobility in mixed alkali glasses apparently resulting in reduced plastic flow in indentation. In addition the literature indicates that alkaline earths also play an important role in controlling the mechanical properties.…”

“…Alternatively the presence of smaller and mobile alkaline earth ions (Mg 2+ ) rather than larger less mobile alkaline earth ions (Ca 2+ , Sr 2+ or Ba 2+ ) might increase plastic flow, and consequently fracture toughness as observed for mixed alkali silicate glasses 7 .…”

Bombardment Induced Transport of Rb+ through a K+ Conducting Glass vs. K+ Transport through a Rb+ Conducting Glass

“…The most prominent consequence is the conductivity exhibiting a minimum for a specific composition [6][7][8][9]. However, also mechanical properties of the material depend critically on the composition [10].…”