Processing of yttrium-doped barium zirconate for high proton conductivity

The factors governing the transport properties of yttrium-doped barium zirconate (BYZ) have been explored, with the aim of attaining reproducible proton conductivity in well-densified samples. It was found that a small initial particle size (50–100 nm) and high-temperature sintering (1600 °C) in the presence of excess barium were essential. By this procedure, BaZr_0.8Y_0.2O_3−δ with 93% to 99% theoretical density and total (bulk plus grain boundary) conductivity of 7.9 × 10⁻³ S/cm at 600 °C [as measured by alternating current (ac) impedance spectroscopy under humidified nitrogen] could be reliably prepared. Samples sintered in the absence of excess barium displayed yttria-like precipitates and a bulk conductivity that was reduced by more than 2 orders of magnitude.