Barium (Zinc) Borosilicate Sealing Glass and Joining Interface with YSZ Electrolyte and Crofer22APU Interconnect in SOFCs

This work describes the performance of two glass-ceramic compositions, BaO-SiO2-B2O3 (Barium borosilicate glass: BaBS) and BaO-ZnO-SiO2-B2O3 (Barium zinc borosilicate glass: BaBS−Zn), used for joining YSZ ceramic electrolytes and Crofer22APU metallic interconnects in solid oxide fuel cells (SOFCs) working at 800°C for 50 h. ZnO had a negative effect on the thermal expansion coefficient (TEC) value of the BaBS-Zn glass-ceramic. XRD and SEM results revealed the formation of rod-shaped barium zinc silicate crystalline phases in the BaBS-Zn glass, which was accompanied by cracks and poor adherence at the YSZ/BaBS-Zn joint interface after working at 800°C for 50 h. The formation of cracks parallel to the interface between the Crofer22APU interconnect and the BaBS-Zn glass-ceramic sealant was observed due to the severe TEC mismatch. The BaBS glass–ceramic adhered well to the YSZ electrolyte as well as the pre-oxidized Crofer22APU without cracks. Chromium oxide scale developed between the pre-oxidized Crofer22APU/BaBS glass-ceramic joint interface with increasing the pre-oxidation temperature. This study shows that BaBS glass-ceramic is more effective than BaBS-Zn as a sealant for joining YSZ electrolytes and Crofer22APU metallic interconnects in SOFCs working at 800°C for 50 h.