Comparison of mechanical, electrical and chemical stability of BaCe0.7Zr0.1Y0.2O3-δ (BCZY7)-(Li/Na)2CO3 proton conductive composite electrolytes fabricated by mechanical mixing and infiltration methods

In the present work, the effect of fabrication method on mechanical strength, chemical stability of BaCe0.7Zr0.1Y0.2O3-δ (BCZY7)-(Li/Na)2CO3 composite electrolyte with proton conductivity, is studied. The composite electrolytes were fabricated by mixing carbonate and BCZY7 powders, synthesized in a solid state reaction, and shaping plus sintering. They also were fabricated by floating a porous BCZY7 scaffold in a molten of carbonate phase. To produce BCZY7 porous scaffold, starch powder was use as pore former. After preparing the composite electrolytes by the two mentioned methods, their mechanical, electrical and chemical stability were investigated. Analytical methods used in this study were included XRD and SEM. Mechanical strength of the fabricated composite electrolytes were determined by using ring on ring method and measuring electrical conductivity as a function of temperature were carried out by using an impedance analyzer. Results proved that, although distribution of carbonate phase in the composites fabricated by mechanical mixing is more uniform than that of the composites fabricated by infiltration process, but their mechanical strength is lower. The results also showed that chemical stability of the composite fabricated by mechanical mixing is higher, which can be due to its lower remained porosities and better distributed of carbonate phase in these composites. The results by impedance analysis and showed that electrical conductivity of the composites fabricated by mechanical mixing and sintering, in the temperature range of 500 to 700 oC is higher. Ionic conductivity of these composites, including 54 vol.% carbonate phase, at 700 oC in air determined as 0.635 s.cm-1.