Electrochemical synthesis and thermal decomposition of zirconia gels containing various metal ions

Abstract

Zirconia gels containing various metal ions have been obtained by cathodic electrolysis at –1.8 V (vs. Ag/AgCl) of an aqueous solution of zirconyl chloride containing 10 mol% Ca, Mg, Y or Ce chlorides. The electrochemically produced gels were deposited on a Pt cathode as a viscous gel or solid. The thermal decomposition of the freeze-dried gels was followed by simultaneous thermogravimetry–differential thermal analysis–mass spectroanalysis (TG–DTA–MS) and X-ray diffraction (XRD). It was found that the gels decompose in three steps with evolution of water and hydrogen chloride. The gels were amorphous at room temperature, but changed to cubic or tetragonal phases at 600 °C. Transformation to the monoclinic or mixed tetragonal and monoclinic phases occurred at 1000 °C in all materials except the Ce-containing samples which formed only a tetragonal phase.