Synthesis of pure and yttria fully stabilized zirconia powders by hydrolysis of tetra n-butyl zirconate

Ultrafine powders of pure zirconia and 9 mole % yttria stabilized zirconia have been synthesized by hydrolysis of tetra n-butyl zirconate in aqueous solutions. In the pure zirconia reaction, a white amorphous powder is obtained. Weight loss studies indicated the amorphous powder is zirconium hydroxide. The hydroxide starts decomposing at 168 degrees C forming cubic zirconia at temperatures higher than 290 degrees C. Above 300 degrees C the cubic zirconia transforms to a tetragonal phase. The tetragonal zirconia is stable beyond 732 degrees C. In the hydrolysis of tetra n-butyl zirconate with a water solution of yttrium acetate to produce the yttria-stabilized zirconia precursor, an amorphous coprecipitated hydroxide of yttrium and zirconium is formed. The white amorphous powder decomposes to the cubic zirconia at temperatures similar to that of the pure zirconia. Yttria stabilized cubic zirconia has a particle size range from 20 nm to 500 nm. Particle growth has been observed for the tetragonally transformed pure zirconia at a temperature as low as 462 degrees C. Compacts of the coprecipitated powder have been sintered in rf plasmas to a density greater than 98% of the theoretical value in 2.5 minutes