Influence of ZnO addition on the properties of high temperature proton conductor Ba1.03Ce0.5Zr0.4Y0.1O3−δ synthesized via citrate–nitrate method

The effect of various amounts of ZnO addition on the densification behavior, electrical conductivity and chemical stability of high temperature proton conductor Ba1.03Ce0.5Zr0.4Y0.1O3−δ synthesized through citrate–nitrate method was investigated. Small amount of ZnO could considerably promote the densification process and the grain growth of Ba1.03Ce0.5Zr0.4Y0.1O3−δ. Samples with 0.5 wt.% ZnO achieved a relative density of 95.6% at 1250 °C, great higher than that without ZnO addition (50.4%). Field emission scanning electron microscopy observation revealed that ZnO addition led to the segregation of Y2O3 from the matrix. Part of ZnO existed at the grain boundary, its role was to form a eutectic melt to promote the densification process. A small part of ZnO dissolved into the lattice, which should be mainly responsible for the increase of bulk conductivity of Ba1.03Ce0.5Zr0.4Y0.1O3−δ with increasing ZnO level. ZnO also enhanced the grain boundary conductivity and increased the stability of Ba1.03Ce0.5Zr0.4Y0.1O3−δ, especially against boiling water.