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China-Japan Workshop on Solid Oxide Fuel Cells

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

[+] Author and Article Information
Lian Peng

State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, and Graduate University, Chinese Academy of Sciences, P.O. Box 353, Beijing, 100190, P.R.C.

Qingshan Zhu1

State Key Lab of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, P.O. Box 353, Beijing, 100190, P.R.C.qszhu@home.ipe.ac.cn

1

Corresponding author.

J. Fuel Cell Sci. Technol 5(3), 031210 (May 27, 2008) (4 pages) doi:10.1115/1.2930768 History: Received August 14, 2007; Revised January 09, 2008; Published May 27, 2008

## Abstract

The purpose of the present paper is to study the influence of glass composition on the thermal stability in the $SiO2–B2O3–BaO$ 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 $800°C$ for only $8h$, the CTE of the glass increased more than 24%. The change of the CTE value was mainly attributed to the fast crystallization that formed high CTE value phases such as $BaB2O4$ and $Ba2Si3O8$. In order to improve the thermal stability, BaO in Glass A was replaced by $B2O3$ (Glass B) and $SiO2$ (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 $800°C$, 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 $300h$ at $800°C$. 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.

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## Figures

Figure 1

Thermal expansion behaviors of Glass A together with those of 8YSZ and NiO-8YSZ (heating rate of 10°Cmin−1 in air)

Figure 2

Variation of CTE values (RT–500°C) with annealing time at 800°C for Glass A

Figure 3

XRD results of Glass A annealed at 800°C for various times

Figure 4

SEM micrograph of the Glass A surface after being annealed at 800°C for 8h; (a) a low magnification and (b) a high magnification of marked area in (a)

Figure 5

Thermal expansion behaviors of Glasses A–C together with those of 8YSZ and NiO-8YSZ (heating rate of 10°Cmin−1 in air)

Figure 6

Variation of CTE values (RT–500°C) with annealing time at 800°C for Glasses A–C

Figure 7

XRD patterns of Glass B after being annealed at 800°C for various times

Figure 8

A SEM micrograph of the Glass B surface after being annealed at 800°C for 20h.

Figure 9

XRD patterns of Glass C after being annealed at 800°C for various times

Figure 10

A SEM micrograph of the Glass C surface after being annealed at 800°C for 300h

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