Sinterability of spinel (MgAl2O4)-zirconia composite powder prepared by double nozzle ultrasonic spray pyrolysis

Two kinds of spinel (MgAl2O4)-zirconia (ZrO2) composite powders were prepared by double nozzle ultrasonic spray pyrolysis; the aqueous solutions in the Mg(NO3)(2)-Al(NO3)(3) and ZrOCl2-YCl3 systems were spray-pyrolysed in a hot zone of an electric furnace heated at 900 degrees C, using two ultrasonic vibrators. The compositions of the composite powders were as follows: (1) Sample No. 1: MgAl2O4 93.36 mol% and yttria-stabilized tetragonal ZrO2 poly-crystals (Y-TZP) 6.64 mol% and (2) Sample No. 2: MgAl2O4 75.51 mol% and Y-TZP 24.49 mol%. While MgAl2O4 and Y-TZP were present in both powders, MgO was additionally detected from Sample No. 2; such MgO disappeared when it was heated up to 1100 degrees C or higher. The composite powders contained spherical particles with diameters of below 2 mu m and, in part, acicular particles with long axis lengths of 1 to 2 mu m. The wet-milled powder of Sample No. 1 showed an excellent sinterability; when the composite powder compact was fired at 1700 degrees C for 10 h, the relative density attained 97.6%. Copyright (C) 1996 Elsevier Science Ltd