INFLUENCE OF CALCINATION TEMPERATURE ON THE PROPERTIES OF SPRAY-DRIEDALUMINA-ZIRCONIA COMPOSITE POWDERS

Alumina-zirconia composite powders containing 10, 12.5, 15 or 20 wt % zirconia were prepared by spray-drying the hydroxide gels. These powde rs were calcined at 650 and 950 degrees C. The spray-dried as well as the calcined powders were characterized by means of Coulter counter, S orptometer, infrared spectroscopy (i.r.), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Initially the spray-dried powders are amorphous and spherical in shape with a diameter of 6 mu m a nd crystallize after calcination treatmen t at 950 degrees C. Sintered density of the 950 degrees C calcined pow der com pacts was higher than 650 degrees C calcined powder compacts. Compacts made from 650 degrees C treated powders retained 100 % tetrag onal phase after sintering irrespective of composition. Some amount of tetragonal phase is transformed into monoclinic phase in the composit es containing higher amount of zirconia in the sintered compacts made from 950 degrees C calcined powders.