Grain morphology memory : yttria as a study case

Jean-Marc Heintz (1) , Agnès Dupont (1, 2) , Claude Parent (1) , Bruno Le Garrec (2) , Philippe Guionneau (1) , Jean Etourneau (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 CESTA - Centre d'études scientifiques et techniques d'Aquitaine

This work shows how it is possible to orientate powder grain morphology characteristics through synthesis conditions both for as-synthesized powders (T = 115°C) and for calcined powders (T = 800 or 1100°C). The chosen example deals with the synthesis of fine yttria powders, using chemical methods. As a first point of interest, the preparation of the as-synthesized powder is discussed. A sol-gel method has been developed in which the chemical nature of the yttrium chelating agent and the [chelating agent/Y] relative concentration are the two main parameters. Depending on these conditions, very different grain morphologies were obtained, needles, platelets, gel-like, in relation to the chemical and structural composition of these precursor powders. The second point of interest deals with the morphology of the yttria powder obtained after thermal treatment of these precursors at high temperature. In some cases, the original morphologies were maintained all over the calcining treatment whereas chemical composition changes were large. Thermodynamics consideration are also proposed to explain the final grain evolution at 1100°C. This yttria study case shows that a "memory effect" can actually be observed all over a large temperature range when the synthesis conditions constrain enough the precursor grain formation from a chemical and structural point of view

Mots clés: Chemical synthesis; Grain shape; Topochemistry; Yttria

Domaines: Matériaux

Jean-Marc Heintz, Agnès Dupont, Claude Parent, Bruno Le Garrec, Philippe Guionneau, et al.. Grain morphology memory : yttria as a study case. Key Engineering Materials, 2004, 264-268, pp.15-20. ⟨10.4028/www.scientific.net/KEM.264-268.15⟩. ⟨hal-00159884⟩