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

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.