Synthesis of porous yttria-stabilized zirconia microspheres by ultrasonic spray pyrolysis

High yield synthesis of yttria-stabilized zirconia (YSZ) porous microspheres can enable application in advanced thermal barrier coatings, exploiting reflective properties originated from high temperature photonics. The complexity of typical wet-chemistry processes utilized in microspheres manufacturing limits yield and can hardly deliver stable porous structures. Here, ultrasonic spray pyrolysis was utilized to produce high quantities of porous YSZ. Droplets of an aqueous precursor solution were dragged with continuous air flow into a furnace kept at temperatures varying from 700 to 1200 °C. Spherical fully cubic zirconia particles were obtained in all processing conditions, and the sizes of the spheres decreased as a function of the processing temperature, ranging from 484 to 373 nm (average diameters), while their crystallite sizes had an inverse trend, ranging from 4.9 to 25.2 nm. This was attributed to higher temperatures activating coarsening of the spheres.