Nanostructured Yttria Powders Via Gel Combustion

Nanostructured yttria powders were prepared by a gel combustion technique. The technique involves exothermic decomposition of an aqueous citrate-nitrate gel. The decomposition is based on a thermally induced anionic redox reaction. A variety of yttria powders with different agglomerate structures can be made by altering the citrate-nitrate ratio γ. The gel with γ = 0.098 in situ yields nanostructured yttria powder at 258 °C that is porous and agglomerated with an average of 25 nm primary particles. Its specific surface area is 55 m²/g. The decomposition of the gels was investigated by simultaneous thermogravimetry analysis (TGA) and differential thermal analysis (DTA) experiments. The produced ashes and calcined powders are characterized by x-ray diffraction (XRD), ir spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer, Emmett, and Teller (BET) analysis.