Alkali diffusivity in alkaline earth sodium boroaluminosilicate glasses

• We investigate the Na–K interdiffusivity in a series of boroaluminosilicate glasses.
• Alkali mobility is maximized when sodium acts as a charge compensator for B or Al.
• Effect of alkaline earth cations on alkali mobility depends on the Al/Na ratio.
• Results are useful for optimizing base glass compositions to tailor alkali mobility.

Understanding the fundamentals of alkali diffusion in boroaluminosilicate glasses is of critical importance for advanced glass applications, where the alkali diffusivity should be either enhanced or reduced. Here, we investigate the sodium–potassium interdiffusivity in thirty-six alkaline earth sodium boroaluminosilicate glasses with varying Si/Al ratio and type of alkaline earth cation by ion exchange experiments. The alkali mobility is maximized when Na+ acts as a charge compensator to Al3 + or B3 + in the glass rather than as a creator of non-bridging oxygen. In the peralkaline regime, the larger alkaline earth cations significantly slow down the motion of alkali ions, while this effect is much smaller in the peraluminous regime. Generally, there is a larger effect of increasing temperature on diffusivity for the larger alkaline earth cations than for the smaller ones.