Yttrium Dopants in Titania: Not Structurally Incorporated but Bound at Surfaces

Structurally incorporated impurities have been shown to have systematic effects on the rate of the thermally driven transformation in titania nanoparticles [1-4]. The anatase-to-rutile transformation is slowed when anatase nanoparticles are doped with a cation of valence > +4, but favored when the valence < +4. Based on these observations, Y dopants should promote the anatase-to-rutile transformation. However, prior studies showed that the transformation is inhibited by Y impurities [1,2], without explaining this observation. In a study led by the scientists of University of California Berkeley and Lawrence Berkeley National Laboratory, extended x-ray absorption fine structure (EXAFS) experiments on yttrium-doped titania nanoparticles were conducted for determining the local structural environment of Y impurities. The experiments were developed in collaboration with SSRL beamline scientists at BL 10-2 and 11-2.