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.

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