Preparation of ZrO₂ powders by oxalate precipitation

Ultrafine ZrO₂ powder was prepared by the decomposition of zirconium oxalate which was precipitated from soluble zirconium salts with proper amount of H₂C₂O₄ or from zirconium oxalate solution with NH₄OH. It was found that the powders obtained could be amorphous, microcrystalline and crystalline Zr(C₂O₄)·4H₂O, according to the different procedures. Metastable tetragonal ZrO₂(t-ZrO₂) formed when differently treated precipitates were calcined at 420°C, but the temperatures at which t-ZrO₂ transformed to monoclinic ZrO₂(m-ZrO₂) were different from each other for differently obtained powders. Particle sizes, morphology and agglomeration states were also process dependent. Non-agglomerated ZrO₂ powder was obtained with alcohol washed powder with its particle size equal to 20 nm at 600°C.