Structural, thermal and electrical properties of Bi and Y co-doped barium zirconium cerates

Bismuth- and yttrium-co-doped barium cerates were successfully synthesised by solid-state reactions followed by sintering between 1,400 and 1,500 °C for 1 to 6 h allowing densification above 98 % to be obtained. All samples were found to retain their original orthorhombic structure after treatment in either oxidising or reducing atmospheres (dry and wet). Mechanical strength was affected by structure upon reduction due in part to strains and stresses induced by bismuth ionic size variations. Conductivity values as high as 0.055 S/cm were obtained for sample BaCe_0.6Zr_0.1Y_0.1Bi_0.2O_3-δ and of 0.0094 S/cm for the Zr-free compound BaCe_0.7Y_0.2Bi_0.1O_3-δ at 700 °C in air. In all the investigated materials, sample BaCe_0.6Zr_0.1Y_0.1Bi_0.2O_3-δ exhibits the highest conductivity in both air and wet 5 % H₂/Ar with good mechanical strength. BaCe_0.6Zr_0.1Y_0.1Bi_0.2O_3-δ is a promising mixed H⁺/e^- conductor, a potential component of composite anode for solid oxide fuel cells.