Precipitation of ultrafine powders of zirconia polymorphs and their conversion to $MZrO_3 (M = Ba, Sr, Ca)$ by the hydrothermal method

Kutty, TRN and Vivekanandan, R and Philip, Sam (1990) Precipitation of ultrafine powders of zirconia polymorphs and their conversion to $MZrO_3 (M = Ba, Sr, Ca)$ by the hydrothermal method. In: Journal of Materials Science, 25 (8). pp. 3649-3658.

PDF Precipitation_of_ultrafine_powders_of_zirconia_polymorphs_and_their_conversion.pdf Restricted to Registered users only Download (1MB) | Request a copy

Abstract

Ultrafine powders of $ZrO_2$ with a high degree of crystallinity and chemical purity are hydrothermally precipitated from aqueous solutions of impure zirconyl oxychloride or the acid extract of zircon $(ZrSiO_4)$-frit at 2 to 8 MPa and 180 to $230^0C$. Monoclinic $ZrO_2$ is produced from aqueous hydrochloric acid, whereas tetragonal $ZrO_2$ is formed from the same medium when sulphate ions are present with $[SO_4^{2-} ]/[Cl–] \geq$ 0.08. If cation impurities such as $Y^{3+}$ or $Ce^{3+}$ are incorporated, the stability range of the tetragonal phase is extended to higher temperatures. Ultrafine powders are characterized by X-ray broadening methods, TEM and thermally as well as mechanically induced transformation characteristics. The tetragonal $ZrO_2$ powder is constituted of polydomain crystallites with higher hydroxyl ion content than the monoclinic phase. Both series of powders convert to $BaZrO_3, SrZrO_3 or CaZrO_3$ perovskites when suspended in the corresponding hydroxide solution at 190 to $480^0C$ and 2 to 100 M Pa.

Item Type:	Journal Article
Publication:	Journal of Materials Science
Publisher:	Chapman and Hall Ltd.
Additional Information:	Copyright of this article belongs to Chapman and Hall Ltd.
Keywords:	ultrafine powders;zirconia polymorphs;hydrothermal method
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	04 Dec 2007
Last Modified:	19 Sep 2010 04:41
URI:	http://eprints.iisc.ac.in/id/eprint/12723

Actions (login required)

View Item