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 Ba_0.95K_0.05Zr_0.85Y_0.11Zn_0.04O_3-d 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 Ba_0.95K_0.05Zr_0.85Y_0.11Zn_0.04O_3-d pellet was used as electrolyte and platinum electrodes. © 2009 Elsevier Inc. All rights reserved.