Crystallization Kinetics of a Solid Oxide Fuel Cell Seal Glass

Abstract

Crystallization kinetics of a barium calcium aluminosilicate glass (BCAS), which is being investigated as a sealant material for planar solid oxide fuel cells, has been investigated by differential thermal analysis (DTA). From variation of DTA peak maximum temperature with heating rate, the activation energy for glass crystallization was calculated to be 259 kJ/mol. Development of crystalline phases, on thornal treatments of the glass at various temperatures, has been followed by powder x-ray diffraction. Microstructure and chemical composition of the crystalline phases were investigated by scanning electron microscopy and energy dispersive spectroscopic analysis. BaSiO 3 and hexacelsian (BaAl 2 Si 2 O 8 ) were the primary crystalline phases whereas monoclinic celsian (BaAl 2 Si 2 O 8 ) and (Ba x , Ca y )SiO 4 were also detected as minor phases. Needle-shaped BaSiO 3 crystals are formed first, followed by the formation of other phases at longer times of heat treatments. The glass does not fully crystallize even after long term heat treatments at 750-900°C.