The Development of Thermally Stable Sealing Glass in the BaO–B2O3–SiO2 System for Planar SOFC Applications

The purpose of the present paper is to study the influence of glass composition on the thermal stability in the SiO(2)-B(2)O(3)-BaO system, and three glasses were consequently investigated. Although Glass A has a coefficient of thermal expansion (CTE) that shows the best match with those of anode and electrolyte materials of solid oxide fuel cells (SOFCs), the thermal stability of Glass A is quite poor where after being heat treated at 800 degrees C for only 8 h, the CTE of the glass increased more than 24%. Them change of the CTE value was mainly attributed to the fast crystallization that formed high CTE value phases such as BaB(2)O(4) and Ba(2)Si(3)O(8). In order to improve the thermal stability, BaO in Glass A was replaced by B(2)O(3) (Glass B) and SiO(2) (Glass C). It was found that the decrease in the BaO content improved the thermal stability of the resultant glasses. Glass B showed less than 8% change of the CTE during annealing time at 800 degrees C, while Glass C exhibited superior long-term. thermal stability, where the change of the CTE was within the equipment detection limit after being heat treated for 300 It at 800 degrees C. The good thermal stability of Glass C was believed to be due to the formation of a more compact glass network after the substitution as compared with that of Glass A. The good thermal. stability makes Glass C attractive to be used as the sealing material for SOFC applications.