THE INFLUENCE OF CRYSTALLIZATION AND WASHING MEDIUM ON THE CHARACTERISTICS OF NANOCRYSTALLINE Y-TZP

A zirconia-yttria gel, made by coprecipitation, was treated in six dif ferent ways to obtain a nanocrystalline Y-TZP powder: one large gel ba tch was split into six parts of which one was crystallized in air and the other crystallized either in water with a high pH or in methanol. The batches were subjected to several post treatments. Powder properti es and densification characteristics of the six powder batches obtaine d in this way are described. The air-calcined powder can be sintered t o a relative density of about 93% at 1070 degrees C/10 h, but reproduc ibility of the sintering characteristics is poor. Optimal hydro-therma l treatment of the powder yields a reproducible sintering process, res ulting in a relative density of 96% at 1070 degrees C/10 h and an aver age grain size between 120 and 130 nm.