Modifications of poled silicate glasses under heat treatment

Abstract

Compositional and structural modification of the subanodic region of poled soda-lime glass under secondary heat treatment is studied using secondary ion mass spectrometry and micro-Raman techniques. A relaxation of the layered compositional distribution in the poled region of the glass remits to more equilibrium state in 250–780 °C temperature range, and the different relaxation mechanisms replace (and supplement) each other as the temperature rises. The main relaxation mechanism below the glass transition temperature, TG, is alkalis – hydrogen ions exchange, while at temperatures up to ~100 °C above TG the main mechanism is the drift of alkali ions. At higher temperatures, up to 780 °C, the drift of calcium ions dominates. Heating the poled glass up to 780 °C results in partial crystallization of the subsurface layer of the poled glass with the formation of micron-size grains, supposedly monoclinic dicalcium silicate, β-Ca2SiO4.