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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.

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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
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.ernet.in/id/eprint/12723

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