Compositional Trends in Photoelastic Constants of Borate Glasses

The stress‐optical coefficients of binary and ternary borate glasses were measured and the factor (p·q), where p and q are the Neumann strain‐optical coefficients, was determined. As a modifier oxide was added to B2O3 glass, the stress‐optical coefficient decreased monotonically. It was found that the stress‐optical coefficient is determined mainly by the elastic modulus, but the factor (p·q) becomes significant when the content and polarizability of the modifier cation are high. It was also found that the factor (p·q) decreases when the content and polarizability of the modifier cation increase. The (p·q) was divided into the lattice effect and the atomic effect, and their compositional dependences were discussed.