Proton conductivity of potassium doped barium zirconates

Potassium doped barium zirconates have been synthesized by solid state reactions. It was found that the solubility limit of potassium on A-sites is between 5% and 10%. Introducing extra potassium leads to the formation of second phase or YSZ impurities. The water uptake of barium zirconates was increased even with 5% doping of potassium at the A-site. The sintering conditions and conductivity can be improved significantly by adding 1 wt% ZnO during material synthesis. The maximum solubility for yttrium at B-sites is around 15 at% after introducing 1 wt% zinc. The conductivity of Ba0.95K0.05Zr0.85Y0.11Zn0.04O3−δ at 600 °C is 2.2×10−3 S/cm in wet 5% H2. The activation energies for bulk and grain boundary are 0.29(2), 0.79(2) eV in wet 5% H2 and 0.31(1), 0.74(3) eV in dry 5% H2. A power density of 7.7 mW/cm2 at 718 °C was observed when a 1 mm thick Ba0.95K0.05Zr0.85Y0.11Zn0.04O3−δ pellet was used as electrolyte and platinum electrodes.