Properties of yttrium-doped barium zirconate ceramics synthesized by the oxidant-peroxo method

摘要

Polycrystalline powders of yttrium-doped barium zirconate with nominal composition BaZr_(0.9)Y_(0.1)O_(3-δ) (BZY10) were synthesized by the oxidant-peroxo (OP) method using hexahydrated yttrium nitrate, barium nitrate and hydrated zirconyl nitrate. This is an environmental friendly method, free of common contaminants such as carbon graphite or halides, and promotes the formation of stoichiometric powders composed by sintcractive nanoparticies. The powders were amorphous and required a heat treatment to crystallize the perovskite phase. The powders were characterized by thermogravimetry and differential thermal analysis, X-ray fluorescence spectroscopy, X-ray diffraction, evaluation of specific surface area by inert gas adsorption, scanning electron microscopy and electrochemical impedance spectroscopy. Stoichiometric single perovskite BZY10 powders were successfully synthesized. Carbonate ions, adsorbed during the powder synthesis, are fully decomposed after calcination at 1200 °C. The powders consist of agglomerate reactive nanosized particles. Pressing the powders to pellets and sintering at 1600 °C yielded relative density higher than 91% of the theoretical density. Scanning electron microscopy images of chemically and thermally etched surfaces clearly defines two regions: one dense with grains of irregular shapes and average submicron size, and another porous. The impedance spectroscopy analysis shows that sintered pellets prepared with OP powders have higher electrical conductivity than pellets using powders obtained by solid state reaction.