Thermo-optic properties of B2O3 doped Li2O–Al2O3–SiO2 glass–ceramics

Abstract Reduction in the temperature coefficient of the optical path length, d S /d T of Li 2 O–Al 2 O 3 –SiO 2 glass–ceramics with near-zero thermal expansion coefficient was attempted using control of the temperature coefficient of electronic polarizability, ϕ , and the thermal expansion coefficient, α . The d S /d T value of 2.6 mol% B 2 O 3 -doped glass–ceramic was 12.5 × 10 −6 /°C, which was 0.9 × 10 −6 /°C smaller than that of B 2 O 3 -free glass–ceramic. On the other hand, reduction in d S /d T through B 2 O 3 doping was not confirmed in precursor glasses. Results showed that reduction in d S /d T of the glass–ceramic through B 2 O 3 doping is caused by the reduction in ϕ . The reduction in ϕ from B 2 O 3 doping was probably attributable to numerical reduction in non-bridging oxide ions with larger ϕ value by the concentration of boron ions in the residual glass phase. In addition, application of hydrostatic pressure during crystallization was effective to inhibit precipitation of β -spodumene solid solution, which thereby decreases d S /d T . The d S /d T value of B 2 O 3 -doped glass–ceramic crystallized under 196 MPa was 11.7 × 10 −6 /°C. That value was slightly larger than that of silica glass. The α value of this glass–ceramic was smaller than that of silica glass.