Barium silicates have been investigated as high-expansion components of solid oxide fuel cells (SOFCs) and, therefore, their synthesis and expansion have been the subject of intensive research in recent years. In this article, we briefly present a new process to make glass–crystalline composites, as well as two novel findings related to a synthesis route of sanbornite (BaSi₂O₅) and the fast in situ formation of a high-expansion sanbornite composite from a Pyrex-type glass powder. The low-temperature synthesis, composition, and expansion of one type of novel glass composite are described. The composites are made by the reaction of BaCO₃ and Pyrex-type powders at 850–950 °C for a short time of one hour. The composites are well sintered and hard, and their linear coefficient of thermal expansion is about 12.3 × 10⁻⁶ C⁻¹. The crystalline-phase formation, dilatometer measurements, SEM data, and possible applications of the composites are presented and discussed.

A mixture of barium carbonate and Pyrex-type powders was heat treated at 500°C-950°C temperature range, for 2 hours at each temperature. The course of the reaction was studied by XRD and weight loss analysis. Reaction of barium carbonate with the Pyrex-type glass was detected at 600°C by weight loss analysis. XRD shows formation of various barium silicates starting at 650°C. At high temperature ,850-950°C, only one crystalline phase, sanbornite, was detected. Silica phase related to quartz starts to separate from the Pyrex-type glass at 650-800°C. Another phase of silica, cristobalite, was detected at 750°C only. The separated silica phase is very reactive with barium carbonate, yielding various silicates well below the decomposition temperature of barium carbonate.