Preparation And Properties Of Inorganic Salt Li₂CO₃/BaCe_0.7Zr_0.1Y_0.2O_3-δ Composite Proton Conductors

This work was based on low-temperature proton conductor SOFCs. Effects ofvarious amounts of Li2CO3on sintering behavior, chemical stability andelectrochemical properties of BaCe0.7Zr0.1Y0.2O3-δ(BCZY) were systematicallyinvestigated.BaCe0.7Zr0.1Y0.2O3-δ(BCZY) electrolyte materials were synthesized by acombustion method. XRD results showed that BCZY powders calcinationtemperature must be at1000°C or above in order to obtain a single perovskitestructure of oxide powder. BCZY powders which were synthesized by a combustionmethod had large surface area and high sintering activity.To improve sinterability of the BCZY electrolyte, Li2CO3was added into theBCZY powders with the content of2wt%,2.5wt%,5wt%and7wt%, respectively.BCZY-L series proton conductors were obtained by sintering at1250°C for5h.Experimental results indicated that Li2CO3melted into liquid phase during thesintering process; this liquid phase reduced the sintering temperature and promotedthe materials sintering densification. But excess liquid phase would increase theporosity of the sample, thus reduce the densification process. Samples with2.5wt%Li2CO3(BCZY-L2.5) achieved a relative density of95.2%, much higher than that of74.9%without Li2CO3addition. Under a certain temperature, the samplesconductivity increased with the Li2CO3content increased; The maximum value of theconductivity appeared when adding2.5wt%Li2CO3into the BCZY powders;Continue to increase the Li2CO3adding content the samples conductivity reduced alittle. A total conductivity of1.6×10-2S cm-1for BCZY-L2.5was obtained at700°Cin3%wet hydrogen atmosphere. At the same time, after treatment in boiling water for10h, the structure and properties of BCZY-L2.5remained stable.To assess influence of Li2CO3addition on fuel cell performance, ananode-supported fuel cell with BCZY-L2.5as electrolyte was prepared. Anopen-circuit potential of1.01V, a maximum power density of427mW cm-2and theionic transport number of0.90were obtained at700°C. This investigation indicatesthat BCZY-L2.5is a promising electrolyte for protonic oxide fuel cells.