Densification, Thermostability And Self-healing Properties Of Glass Ceramic For SOFC Seal Material

Solid Oxide Fuel Cell (SOFC) is a device that can convert chemical energy directlyinto electrical energy with high efficiency and low pollution. There are two basic designsfor SOFC applications: tubular and planar. Compared with tubular designs, planardesigns have significant advantages including lower cost and higher power densities.However, hermetic seal is one of core technicals for commercial application. Therefore,it is necessary to optimize the application process parameters for the comprehensiveperformance of seal materials to meet seal requirement, and to develop the new sealmaterials.Firstly, With different particle sizes(3.94μm、6.82μm、27.98μm and39.09μm) anddifferent pressures(5MPa、10MPa、15MPa and20MPa), the densification sintered ofgreen tablet were investigated in35mol%(SrO+La2O3)-5mol%Al2O3-60mol%SiO2forp-SOFC. The line shrinkage and volμme density of sintered tablet were calculated, andthe microstructure of fracture surface was observed by SEM. With the same particle size,the line shrinkage of sintered tablet is maximμm with the pressure of5MPa, and thevolμme density is maximμm with the pressure of20MPa.Secondly,26mol%SrO-26mol%CaO-4mol%B2O3-(44-x)mol%SiO2-xmol%GeO2(x=0，11，22，33and44；SCBSG) is investigated. CTE, HSM, electric insulation, chemicalcompatibility and thermal stability were studied by thermal dilatometer, heatingmicroscope, electrochemical workstation, sweep electron microscopy, comprehensivethermal analyzer and X-ray diffractometer. The interface of seal glass and8YSZelectrolyte is distinct. Inversion temperature and crystal peak tempter are665℃～737℃and731℃～851℃. In the SCBSG glass system, the CTE is9.9×10-6K-1～11.2×10-6K-1,operating temperature is850℃～950℃, impedance and conductivity(logσ) isrespectively106～107·cm2and-5.2～-8.0. Crystallization activation energy is366.91kJ/mol～422.80kJ/mol. As seal material of p-SOFC, SCBSG glass system has thepossible potential.Finally, Ca0.7Sr0.3GeO3crystalline phase of low melting point was found in thequarter. Melting temperature is997.5℃, between987℃(CaB4O7) and1122℃(CaB2O4),which are appropriate for p-SOFC healing ceramic seal. Ca0.7Sr0.3GeO3ceramic wassynthesized, whose self-healing property, heat mechanical and heat stability werediscussed. Ca0.7Sr0.3GeO3ceramic material had good self-healing performance, heatingfrom room temperature to900℃with the rate of40℃/min. After heat cycle of60times,combine interface of seal glass and8YSZ electrolyte (anode supported type) is stable.During the oxidation and reduction atmosphere of dry and30vol%water vapour at800℃ for28days, weight loss was0.45±0.05mg·cm-2～3.26±0.73mg·cm-2. The seal-heatingceramic material is potential for the application of p-SOFC.