Crystallization behaviour, structure and properties of sintered glasses in the diopside–Ca-Tschermak system

Four glasses with nominal compositions of CaMg0.8Al0.4Si1.8O6, CaMg0.75Al0.5Si1.75O6, CaMg0.7Al0.6Si1.7O6, and CaMg0.65Al0.7Si1.65O6, were successfully obtained by melting in alumina crucibles at 1580 °C for 1 h, aiming at producing glass ceramics based on diopside–Ca-Tschermak. Sintering and crystallization behaviour of the glasses, coupled with calculation of the activation energy of crystallization, were investigated upon heat treatment under different conditions of heating rates (5–40 K/min), temperatures (850–1000 °C), and times (1–300 h). The experimental results showed that there is a threshold of Ca-Tschermak solubility in diopside structure at ca. 30 mol.%, which is technologically important with regard to the production of mono-mineral glass ceramics. The good matching of thermal properties and the strong adherence to yttria stabilized cubic zirconia indicate the investigated glass ceramics for further experimentation as candidates for SOFC sealants.