Synthesis and Enhanced Proton Conduction in a 20 mol% Ytterbium Doped Barium Zirconate Ceramic Using Zn as Sintering Aid
Paper in proceedings, 2012
20% Ytterbium(III)-doped perovskite structured barium zirconate, BaZrO3, was prepared by two different synthesis routes: solid state and sol-gel routes. 2 % Zinc(II) was added as an acceptor dopant at the Zr(IV) site according to stoichiometry. It was also added as 2 % excess of the formula. The purpose of this study is to see how zinc(II) acts as a sintering aid in view of synthesis route, densification and conductivity of the material. A dense ceramic (90% of theoretical density) was achieved by the sol-gel method when stoichiometry was adjusted. Phase purity of the samples was checked by X-ray powder diffraction (XRD). Thermogravimetric analysis (TGA) and Impedance spectroscopy (IS) was used to characterize hydration and electrical conductivity respectively. The data shows that the addition of stoichiometric amounts of Zn2+ via sol-gel synthesis route promotes not only densification but also water incorporation and conductivity in comparison with the solid state route, keeping the same final sintering temperature of 1500 degrees C. For example, pre-hydrated BaZr0.78Zn0.02Yb0.2O3-delta, prepared via the sol-gel method shows total conductivity (sigma(tot)) value of 3.14*10(-5) and 3.8 *10(-3) Scm(-1), whereas for the solid state route, sigma(tot) values are 1.74*10(-5) and 8.87*10(-4) Scm(-1) under dry Ar (heating cycle) at 300 degrees C and 600 degrees C, respectively.