T. Settu et R. Gobinathan, SYNTHESIS AND CHARACTERIZATION OF Y2O3-ZRO2 AND Y2O3-CEO2-ZRO2 PRECURSOR POWDERS, Journal of the European Ceramic Society, 16(12), 1996, pp. 1309-1318
Thixotropic gels of the precursor powders of the titled compounds have
been prepared by the addition of oxalic acid to the mixed solutions o
f metal salts at room temperature (approximate to 27 degrees C). The c
lear sols of yttrium-zirconyl oxalate (YZO) and yttrium-cerium-zircony
l oxalate (YCZO) gelled within a few hours and were oven-dried at 40 d
egrees C. The various stages of gelation behaviour of the sols are exp
lained on the basis of DLVO theory. By repeptizing the dried gel powde
rs with water, concentrated sols were prepared. The gelation time as a
function of chloride ion concentration is discussed for both sols. Th
e nature of the temperature dependence of the dried gel powders was st
udied by means of thermogravimetric analysis and differential thermal
analysis. Powder X-ray diffraction was used to study the crystallizati
on behaviour of the dried amorphous gel powders. It is found that thes
e powders crystallize in tetragonal phase when calcined at 850 degrees
C for 1 h. Estimation of surface area and infra-red characterization
have also been carried out for the prepared powders. (C) 1996 Elsevier
Science Limited