The effects of precipitants on co-precipitation synthesis of yttria-stabilized zirconia nanocrystalline powders

Yttrium-stabilized zirconia (Y0.08Zr0.92O1.96, YSZ) nanocrystalline powders were prepared by co-precipitation methods. Different precipitants (ammonium hydroxide, ammonium bicarbonate, oxalic acid, and urea) were used to study the effects of precipitants on co-precipitation synthesis of YSZ nanocrystalline powders. Thermogravimetric analysis-differential scanning calorimetry, powder X-ray diffraction, Fourier-transform infrared, scanning electron microscope, energy-dispersive spectrometer, Brunauer-Emmett-Teller, Barrett-Joyner-Halenda, and X-ray photoelectron spectroscopy analysis methods were employed to investigate the thermal decompositions, phase evolutions, micro-morphologies, surface areas, and elements analysis of the synthesized YSZ precursor powders or nanoparticles. Although different precipitants were used, the calcined products at 600 degrees C have nearly identical chemical compositions. The crystallization temperature of the precursor powders to evolve to cubic phase is the lowest (about 400 degrees C) when ammonium hydroxide is used as a precipitant, while it is about 500 degrees C in the case of other three types of precipitants (ammonium bicarbonate, oxalic acid, and urea) that were used. Ammonium bicarbonate cannot precipitate ZrO2+ effectively in the solution, resulting in the formation of cubic Y0.18Zr0.82O1.91 at 1000 degrees C. Despite the time-consuming co-precipitation process, urea was proved to be the optimal precipitant in terms of the fabrication of nanocrystalline YSZ powders with designed Y/Zr/O molar ratio, large surface area, small crystallite size, and well dispersion. [GRAPHICS] .