Effect of excess Ca2+ on the formation of CaZrO3 powders via polyacrylamide gel method

High-purity perovskite structure orthogonal phase CaZrO3 fine powders were synthesized via a simple, fast, low-cost, and eco-friendly method, known as the polyacrylamide gel (PAG) method. The starting materials are mixed and dissolved in water with a non-stoichiometry ratio of Ca2+/Zr4+ by excess Ca2+. The effects of the excess Ca on the phase formation of CaZrO3 powders were investigated. When the Ca2+ and Zr4+ are reacted with 1:1, 1.05:1 and 1.1:1 stoichiometries, a minor amount of non-stoichiometric calcium-zirconium oxide was frequently observed over the entire range of sintering temperatures from 550 degrees C to 1350 degrees C. Increasing the Ca2+/Zr4+ ratio can contribute to the reduction of non-stoichiometric calcium-zirconium oxide. When Ca2+ and Zr4+ are reacted with 1.15:1 stoichiometry, XRD patterns showed peaks corresponding to high-purity orthogonal-phase CaZrO3 after sintering at 1150 degrees C for 3 h. This result proved that excess Ca2+ contributes to solving the difficulty of removing impurities from CaZrO3 powder.