Effect of Strontium the phase structure of Ba1−xSrxCe0.65Zr0.2Y0.15O3−δ (0≤x≤0.25) proton conductor by citrate–EDTA complexing sol–gel method

•The proton conducting oxides Ba1−xSrxCe0.65Zr0.2Y0.15O3−δ have been successfully synthesized using a sol–gel process.•Increasing Sr content caused lattice contraction and reduction in cell volume up to a doping level of 20%.•Attained highest ionic conductivity value at low sintering temperature with good density for x=0.2 sample.•Relation between conductivity, sinterability, cell volume, tolerance factor and grain size has been discussed. Proton conducting oxides Ba1−xSrxCe0.65Zr0.2Y0.15O3−δ (0≤x≤0.25) are prepared using the citrate–EDTA complexing sol–gel method. The effect of strontium and yttrium doping on the material properties is systematically investigated. The phase formation, thermal analysis, morphology, stability and conductivity measurements are performed on the sintered powders through TG–DTA, XRD, SEM, EDAX, FTIR, Raman and LCR measurements. The results indicated a single-phase orthorhombic system. Strontium incorporation helped in increasing the grain size up to 20% of strontium doping while reducing the lattice parameters and unit cell volume. The ionic conductivities of the Ba1−xSrxCe0.65Zr0.2Y0.15O3−δ sintered oxides increased with increase in the concentration of Sr2+ along with the co-doping strategy of trivalent Y3+ in the B site. Among the synthesized samples, Ba0.8Sr0.2Ce0.65Zr0.2Y0.15O3−δ pellet with orthorhombic structure showed highest conductivity with a value of 2.35×10−1S/cm and 2.41×10−1S/cm at 500°C due to its smaller lattice volume, larger grain size and lower activation energy that led to excessive increase in conductivity. All pellets exhibited good chemical stability when exposed to air and H2O atmospheres. These results indicate that this composition can be used as a potential electrolyte if synthesis conditions and temperature are well maintained.