Development and performance of diopside based glass-ceramic sealants for solid oxide fuel cells

We report on the development and performance of diopside (CaMgSi₂O₆) based glass-ceramic (GC) sealants for solid oxide fuel cells (SOFCs). Ten glass compositions were prepared by various additions and substitutions of La₂O₃, Cr₂O₃ and B₂O₃ in diopside system. The structure of the glasses has been investigated by employing ²⁹Si, ²⁷Al and ¹¹B MAS-NMR spectroscopy. The crystallization kinetics of the glasses has been investigated using differential thermal analysis (DTA) while X-ray diffraction (XRD) in conjunction with Rietveld-RIR technique has been employed to quantify the amount of crystalline and amorphous phases in the GCs. Hot-stage microscopy (HSM) has been used to investigate the influence of La₂O₃ and B₂O₃ on the sintering behavior of the glass powders. The joining and chemical interaction of the B₂O₃ and La₂O₃-containing glasses with Crofer22 APU and Sanergy HT (metallic interconnects for SOFC), has been investigated in humidified reducing atmosphere at SOFC operating temperature while the leak rate of GC sealants has been investigated using oxygen pump leak rate method. The suitable sintering and crystallization behavior of the GCs along with good adhesion to interconnect alloys and low leak rate indicate that the investigated GCs are suitable candidates for further experimentation as SOFC sealants.