PRELIMINARY-RESULTS ON PREPARATION AND SINTERING BEHAVIOR OF HAFNIA POWDERS

In the present work, the characterization and sintering behaviour of h afnia prepared via thermolysis of an oxalic complex compound is invest igated. The chemical formula of the complex is H-2(HfO(C2O4)(2), 5H(2) O). Yttria was added using an acid-base reaction in order to stabilize the hafnium oxide. The pyrolysis of the precursor was conducted using either a controlled calcination schedule or by introducing a chemical media which favours quick reaction. With the last route, the temperat ure rises very quickly. Three batches of hafnia were prepared: pure, p artially and fully stabilized. Morphology of the powders was investiga ted by means of SEM, porosimetric and specific surface area measuremen ts. Then, green samples compacted up to 400 MPa were sintered or hot p ressed in the range 1700-1900 degrees C. The density of sintered sampl es was largely dependent on the synthesis process and on the morpholog y of the green samples. (C) 1997 Published by Elsevier Science Limited .