Structure and photoelastic constant of binary ns2-type metal cation containing silicate glasses

Abstract The photoelastic constant of nominal molar compositions RO(R' 2 O 3 )–SiO 2 (R = Pb, R' = Sb, Bi) decreases with increasing RO and R' 2 O 3 , which is in agreement with calculations based on the quantitative structural information of silicate tetrahedra determined by 29 Si MAS-NMR. Compositional dependence of the photoelastic property is attributed to the electronic polarizabilities of the constituent ions. To understand the relationship between the structure and photoelastic response, the reported electronic polarizability is modified to match the value that includes the observed density and refractive index based on Lorentz–Lorenz eq. A composition of photoelastic glass with zero photoelastic constant is identified by an empirical equation that provides the ratio of the metal‑oxygen bond length to the coordination number. Our finding is that the compositional response in the photoelastic constant is due to the variation in the electronic polarizability, despite the different ns 2 -type metal cations incorporated in the silicate glass.