Crystallization of Sodium Borosilicate Glass with the Addition of Cr2O3

Glass composition of 6Na 2 O 22B 2 O 3 ·70SiO 2 ·2Cr 2 O 3 is studied by scanning electron microscopy, X‑ray powder diffractometry (XRPD), and differential thermal analysis, depending on the duration of heat treatment at a temperature of 550°C. It is established that during heat treatment for 24–96 h, a phase separation structure with interpenetrating phases is formed in the studied glass, and a crystalline phase of eskolaite—Cr 2 O 3 is also formed. With the maximum heat treatment duration of 96 h, cristobalite is formed in the bulk of the glass, which is accompanied by a decrease in the glass transition temperature of the low-viscosity phase. In this case, the intensity of eskolaite peaks decreases. Cr 2 O 3 and SiO 2 crystallize apparently due to the substance of the low-viscosity phase.