PREPARATION AND CHARACTERIZATION OF YTTRIA-STABILIZED ZIRCONIA POWDERS BY SOLVENT-EXTRACTION PROCESS

This study demonstrates that zirconium and yttrium can quantitatively be coextracted with di-(2-ethylhexyl) phosphoric acid or 2-ethylhexyl- phosphonic acid mono-2-ethylhexylester from commercial grade of starti ng materials under suitable conditions, End that both zirconium and yt trium can be stripped completely with oxalic acid from the extractants under some specific conditions. The resulting oxalates, after careful washing with absolute ethanol, may be calcined to both ultrafine and pure yttria-stabilized zirconia powders, while the stripped extractant s can be recycled to extract zirconium and yttrium. The present proces s, therefore, is a more economical technique than the metal alkoxide p rocess - one of the most popular chemical processing routes for the pr eparation of advanced ceramic powder, yet it is a very efficient techn ique for controlling the purity, particle size, and crystalline phase composition of the powders. (C) 1997 Elsevier Science Limited and Tech na S.r.l.