Study On The Doping Modification, Structure And Electrical Properties Of BaSn_0.5Y_0.5O_2.75 High Temperature Proton Conductors

Solid oxide fuel cells (SOFCs) have received considerable attention as a kind ofgeneration device for their high efficiency and low pollution, and using proton conductors aselectrolytes is an important way to realize the intermediate temperature applications of SOFCs.BaSn0.5Y0.5O2.75(BSY) proton conductor possesses high proton conductivity and goodchemical stability in the presence of CO2-containing atmospheres, but its poor sinterabilityand low structural stability under the moist atmospheres greatly limit its applications inSOFCs. In this paper, the doping modification of BSY was carried out by adopting Zn or In inorder to modify its sinterability and mechanical stability. The effect of Zn and In content onthe microstructure, structural stability, sinterability and electrical properties were investigatedby XRD, SEM and EIS analysis methods.BaSn0.46Y0.5Zn0.04O2.75and BaSn0.5Y0.46Zn0.04O2.75-nano proton conductors weresuccessfully synthesized by replacing the Sn and Y of BSY with Zn respectively, and theresults show that BaSn0.5Y0.46Zn0.04O2.75-has a higher density and higher conductivities aftersintered under1350℃for5h. Zn and Y co-doped BaSn0.5Y0.5-xZnxO2.75-(x=0-0.04, BSYZ)nano proton conductors were successfully synthesized by a gel polymerization method, andthe effect of Zn content on the sinterability, microstructure and electrical properties wereinvestigated. The results show that a small amount of Zn doping (≥2mol%) not onlyremarkably decrease the sintering temperature (1350℃) to obtain the dense pellets, but it isalso favorable to promote the grain growth and improve the structural stability under wetatmosphere. At the same time, the conductivities of samples are strongly dependent on the Zncontents, such as the total and grain boundary conductivities increase with the increasingdoping amount of Zn, but the bulk conductivity decreases with the increasing doping amount of Zn. The bulk conductivity of BaSn0.5Y0.48Zn0.02O2.75-is1.41×10-3S/cm at600℃under wetAr atmosphere.In and Y co-doped BaSn0.5Y0.5-xInxO2.75(x=0.2-0.4, BSYIn) nano proton conductorswere successfully synthesized by a gel polymerization method, and the effect of indiumcontent on the sinterability, microstructure and electrical properties of BSYIn wereinvestigated. The results show that the introduction of indium is quite beneficial to theimprovement of the sinterability for BSYIn and the sinterability increases with the increasingindium content, which reduce the sintering temperature (1450℃) to obtain dense materials.Scanning electron microscope (SEM) observations show that the grain size of BSYInincreases with increasing doping amount of indium. In addition, the conductivity of BSYIndecreases with the increasing doping amount of indium. The maximum total and bulkconductivities of BaSn0.5Y0.3In0.2O2.75are1.08×10-3S/cm and2.46×10-3S/cm at600℃undermoist Ar atmosphere respectively.The microstructure, structural stability and electrical property of BSYZ and BSYIn wereinvestigated, and it confirms that both two electrolytes can be good candidate materials forintermediate-low temperature solid oxide fuel cells and have good application anddevelopment prospect.