THE PROPERTIES OF ZIRCONIA POWDERS PRODUCED BY HOMOGENEOUS PRECIPITATION

Spherical particles of zirconia were obtained by the calcination of mo nodisperse oxy-basic zirconium carbonate particles produced by homogen eous precipitation from zirconium sulphate solutions. By varying the s alt concentration, monodisperse powders with diameters of 0.2-3 micron s were obtained. The evolution of the structural characteristics of th ese powders during the calcination process was studied in some detail. The most interesting findings were the development of fully crystalli ne tetragonal zirconia at temperatures as low as 300 degrees C and the existence of the metastable zirconia in domains of up to 100 nm in di ameter. These domains appeared to exhibit a sub-structure of closely o riented nanocrystallites. By comparing powders calcined in air and nit rogen it appeared that the stability of the metastable tetragonal phas e with respect to monoclinic zirconia was enhanced in sub-stoichiometr ic material. The interpretation of measurements of crystallite size an d microstrain by X-ray diffraction is also discussed.