Properties of Hf doped BaZr0.8Y0.2O3-δ protonic conductor

Abstract Chemically stable BaZr0.8Y0.2O3-δ (BZY) is limited to applications because of its poor sintering behavior and low total electrical conductivity. The study aimed to enhance conductivity and sinterability for BaZr0.8Y0.2O3-δ utilizing the partial replacement of Zr4+ with Hf4+. As expected, Hf4+ was doped into the lattice and BaZr0.6Hf0.2Y0.2O3-δ (BZHY) was facilely sintered and reached a relative density above 94.79(2)% at 1600 °C due to Hf4+ doping. The samples were quite dense with integral grains and there were no pores observed from the surface and cross-section. The samples displayed excellent chemical stability in H2, H2S, CO2 and water steam containing atmosphere even in boiling water. Thermogravimetric analysis revealed that BZHY exhibited remarkably enhanced hydration ability over BZY. The electrical conductivities of the samples in different atmospheres were investigated from 300 to 700 °C. Compared with BZY, BZHY sample displayed a higher conductivity under the same conditions due to higher relative density, bigger grain size and better hydration ability. To test the electrolyte applicability, an impedancemetric type H2 sensor consisting of ZnO sensing electrode and BZHY electrolyte was fabricated. The sensor showed excellent sensing performance and response signals varied logarithmically with the H2 concentrations in the range of 200-600 ppm at 600 °C.