A low silica, barium borate glass–ceramic for use as seals in planar SOFCs

A low silica, barium borate glass–ceramic for use as seals in planar SOFCs containing 64 mol%BaO, 3 mol%Al2O3 and 3 mol%SiO2 was studied. Coefficient of thermal expansion (CTE) between 275–550 °C, glass transition temperature (Tg), and dilatometric softening point (Ts) of the parent glass were 11.9 × 10−6 °C−1, 552 °C, and 558 °C, respectively. Glass–ceramic was produced by devitrification heat treatment at 800 °C for 100 h. It was found that nucleation heat treatment, seeding by 3 wt%ZrO2 as glass-composite and pulverization affected the amount, size and distribution of crystalline phases. SEM-EDS and XRD results revealed that crystalline phases presented in the devitrified glass–ceramic were barium aluminate (BaAl2O4), barium aluminosilicate (BaAl2Si2O8) possibly with boron associated in its crystal structure, and barium zirconate (BaZrO3). CTE of the devitrified glass–ceramic was in the range of (10.1–13.0) × 10−6 °C−1. Good adhesion was obtained both in the cases of glass and devitrified glass–ceramic with YSZ and AISI430 stainless steel. Interfacial phenomena between these components were discussed.