Analysis of the surface structure of soda lime silicate glass after chemical strengthening in different KNO3 salt baths

• Glass slides were strengthened in different nominally pure KNO3 salt baths.
• The ion exchange ratio at the surface and the mechanical properties were measured.
• The surface microstructure was inspected by micro-Raman spectroscopy.
• The different glass properties were related to the network microstructure.
• The effects of different nominally pure salts were outlined.

This paper deals with the physico-chemical and mechanical properties of soda lime silicate float glass treated in KNO3 baths with different purity levels. The potassium concentration profile in the surface layers was measured by EDXS and correlated with the residual stress frozen in the material, which was determined by a procedure based on the measurement of the strengthened sample curvature deriving from progressively etching one of its surfaces. This allowed pointing out a significant influence of the used salt. In order to better understand the phenomena and mechanisms underlying the surface equilibrium conditions, micro-Raman measurements were also performed on the glass surface in the aim to investigate the variation of the glass microstructure after ion-exchange in the different salt baths.