Synthesis of Nanosize Yttria-Stabilized Zirconia by a Molecular Decomposition Process

Nanosize yttria-stabilized zirconia (YSZ) was synthesized by a novel approach based on molecular decomposition. In this approach, yttria-doped BaZrO3 (Y–BaZrO3) or yttria-doped Na2ZrO3 (Y–Na2ZrO3) precursors were first synthesized from BaCO3, ZrO2, and Y2O3 or BaCO3 and commercial YSZ for Y–BaZrO3, and from Na2CO3 and YSZ for Y–Na2ZrO3, by a conventional solid-state reaction method. The precursors were then boiled to leach away the unwanted species, BaO or Na2O, either in a dilute HNO3 solution in water in the case of Y–BaZrO3, or in deionized water in the case of Y–Na2ZrO3. During boiling in HNO3 or water, the residue of Zr–Y–O skeleton formed fine, nanosize YSZ particles. The particle size of the assynthesized nanosize powders estimated from X-ray diffraction peak broadening was ~2–3 nm, while that estimated from specific surface area measurements by BET adsorption isotherm was ~15 nm. Examination under a transmission electron microscope showed that the crystallite size was ~5 nm. Samples were also examined by Raman spectroscopy to determine the crystallographic polymorph of the YSZ formed. Subsequent heating in air led to particle growth. However, even when the particles were heated to a temperature as high as 1000°C, the particle size was well in the nanosize range.