Mechanical–Structural Investigation of Ion-Exchanged Lithium Silicate Glass using Micro-Raman Spectroscopy

Abstract

Micro-Raman spectroscopy was used to determine the structural modifications occurring in a simple ion-exchanged glass. The base lithium silicate composition 30Li2O–70SiO2 was studied as it underwent ion exchange, Li+ ↔ K+, at six temperatures spanning the glass transition point. Using a well-developed relationship between the Si–O–Si bond angle, the Si–O bond length, and Raman shifts, the reduction in network molar volume and increase in compressive stress were estimated. On the basis of the effect of the ion-exchange temperature, the existence of a threshold energy below which the compressive stress manifests as the reorientation of silica tetrahedra only and above which the system relaxes by increasing the Si–O bond length is proposed. Finally, the linear network dilation coefficient is revisited in terms of these new data and an explanation given for its underestimation and overestimation of stress at low and high temperatures, respectively.

Mechanical–Structural Investigation of Chemical Strengthening Aluminosilicate Glass through Introducing Phosphorus Pentoxide

“…The chemical strengthening properties of glasses are typically characterized by CS and depth of ion-exchange layer (DOL). Moreover, these properties depend much on glass composition and topological restriction (Smedskjaer et al, 2010;Vargheese et al, 2014;Calahoo et al, 2016). Chemically strengthened aluminosilicate glasses through K + -Na + ion exchange are currently receiving significant interest due to their excellent mechanical properties (Chang et al, 2014).…”

Depth analysis of a compression layer in chemically strengthened glass using depth-resolved micro-Raman spectroscopy

“…This behavior has been also reported in the Li(K) 2 OSiO 2 system. 8) For the non-strengthened glass, on the other hand, the position seems invariant in a range of z = 0135¯m. increases and [Na+K] seems invariant with respect to z, which suggests the NaK ion exchange has been achieved and this behavior is consistent with the previously reported.…”

“…In the ion-exchanged layer, the TO 2 network is compressed due to the ion exchange of Na for the larger ion, K, which results in the compressive stress. 1)3), 8) As for the simple binary silicate glass, Li(K) 2 OSiO 2 , relation between the compressive stress and shifts and fractions of the Raman peaks on the Q n structures in the compressed SiO 2 network has been discussed on the basis of changes in bond angles of SiOSi and bond lengths of SiO. 8) However, that discussion seems difficult to apply to the present work since the present chemically-strengthened glass has more complex composition and structure, particularly Q n structures that comprise the SiO 4 and AlO 4 tetrahedra.…”

“…1)3), 8) As for the simple binary silicate glass, Li(K) 2 OSiO 2 , relation between the compressive stress and shifts and fractions of the Raman peaks on the Q n structures in the compressed SiO 2 network has been discussed on the basis of changes in bond angles of SiOSi and bond lengths of SiO. 8) However, that discussion seems difficult to apply to the present work since the present chemically-strengthened glass has more complex composition and structure, particularly Q n structures that comprise the SiO 4 and AlO 4 tetrahedra. 5), 16) Nevertheless, we can propose a tentative model to give a qualitative and simple explanation for the Raman peak shift around 1100 cm ¹1 by the ion exchange as follows: The ion exchange for the larger ion causes compression of the TO 2 network, as illustrated in Fig.…”

“…4)8) For example, Hödemann et al have proposed a gradient scattered light method in which a laser beam is incident to the glass with a grazing angle through a glass prism attached to the glass surface and determined an depth profile of a compressive stress. 7) Very recently, Calahoo et al have proposed a non-destructive, non-contact method using depth-resolved micro-Raman spectroscopy and obtained the depth profile of a compressive stress from peak positions of the Raman peaks; 8) however, its application has been limited to the simple binary glasses, Li(K) 2 OSiO 2 . In this study, on the other hand, we applied the depth-resolved micro-Raman spectroscopy to Corning Gorilla Glass 3, which is one of the popular, commercialized chemically-strengthened glasses and we investigate relation between the Raman spectra and an ion-exchange rate with a varying depth.…”