Phase-separated structure and properties of glasses in the (16–x)Na2O–14B2O3–70SiO2–xFe2O3 system

Abstract

The effect of Fe₂O₃ on the structure, glass transition temperature, viscosity, and electric resistance of glasses in the (16–x)Na₂O–14B₂O₃–70SiO₂–xFe₂O₃ (x changes from 2 to 10 mol %) system is investigated. It is demonstrated that at a Fe₂O₃ concentration up to and including 4 mol % glasses are single-phased and X-ray-amorphous. When the Fe₂O₃ content is higher than 6 mol %, glasses are characterized with a phase-separated structure with magnetite inclusions. The addition of Fe₂O₃ up to 4 mol % (inclusive) decreases the viscosity and glass transition temperature. Along with the decrease of the Fe₂O₃ content in glasses under study, the electric resistance decreases for all heat treatment conditions by 1–2 orders of magnitude, and the calculated activation energy values are similar to those of sodium-borosilicate glasses without iron.