Study on non-isothermal crystallization kinetics of the BaO-CaO-Al2O3-B2O3-SiO2 glass for IT-SOFCs sealing

Abstract The crystallization ability plays a key role in effecting thermal ability of sealing glass for intermediate temperature-solid oxide fuel cells (IT-SOFCs) to prevent fuel leakage during operation and insulate the cell stack from the external atmosphere. Herein, using differential thermal analysis (DTA) techniques, the growth mode of crystals precipitated in BaO-CaO-Al2O3-B2O3-SiO2 (BCABS) sealing glass through the heat treatment was calculated in terms of non-isothermal crystallization kinetics for the first time. The calculated results showed that the average kinetic exponent n of the glass was approximatively 1, indicating that the crystal nucleuses became to form and further grew with one-dimensional mode from the surface inwards. Scanning electron microscope (SEM) observations clearly revealed that a large number of one-dimensional filamentous crystals have been formed on the interface between the sealing glass and the electrolyte after the heat treatment at 973 K for 100 h, which perfectly coincided with the theoretical calculations, and the glass was well combined with the electrolyte without any visible cracks or peeling at the interface. The one-dimensional growth of hexagonal BaAl2Si2O8 crystals verified by X-ray diffraction (XRD) could effectively decelerate the decrease of thermal expansion coefficient of glass to ensure enhance the thermo-stability of the BCABS sealing glass for IT-SOFC.