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Surface and Bulk Modifications of Nanostructural ZrO2 Powder Induced by Doping with Vanadium and Molybdenum Ions
|Andrzej Adamski 1, Piotr Zapala 1, Pawel Jakubus 2, Zbigniew Sojka 1,3|
1. Jagiellonian University, Faculty of Chemistry, Ingardena 3, Kraków 30-060, Poland
Zirconia and ZrO2-based materials have been widely used in many fields due to their high melting point, low thermal conductivity, high resistance to corrosion and remarkable oxygen transport properties.
In the present studies a nanostructural tetragonal zirconia (t-ZrO2) of enhanced thermal stability with developed surface area and unimodal pore structure, was obtained from ZrOCl2 by modified forced hydrolysis method followed by aging at 100°C for 48 h. Collective XRD, RS, EPR and microscopic SEM/TEM investigations, complemented by N2-sorption measurements, showed that surface and bulk properties of ZrO2 as well as its phase composition are strongly dependent on the presence, nature and concentration of dopants such as vanadium and molybdenum ions. Those additives were deposited on the surface of t-ZrO2 using the classical or slurry impregnation techniques.
As revealed by variable-temperature XRD and EPR measurements, even at temperatures below the Hüttig temperature (i.e. < 800°C), the V and Mo dopants can migrate into the bulk of t-ZrO2, forming the corresponding solid solutions. The observed structural changes were further confirmed by Rietveld refinement, basing on the XRD data. It was found that spontaneous reduction of the surface V5+ and Mo6+ ions and concomitant phase transition from the tetragonal to the monoclinic polymorph of ZrO2, opened channels of facile diffusion of the resultant idiovalent dopant ions into the bulk of the ZrO2 matrix. Final phase composition of the doped ZrO2 materials was determined by the amount of incorporated additives. Vanadium loadings below 3 mol. % stabilized the low-temperature tetragonal polymorph, whereas higher loadings favored its transformation into the monoclinic form.
Presentation: Oral at E-MRS Fall Meeting 2006, Symposium C, by Andrzej Adamski
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-08 13:55 Revised: 2009-06-07 00:44