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 degrees C, glass transition temperature (T-g), and dilatometric softening point (T-s) of the parent glass were 11.9 x 10(-6)degrees C-1, 552 degrees C, and 558 degrees C. respectively. Glass-ceramic was produced by devitrification heat treatment at 800 degrees 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) x 10(-6)degrees 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. (C) 2008 Elsevier B.V. All rights reserved.