10 research outputs found
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Local order in titania polymorphs
Crystalline structure local order of titania polymorphs, brookite, anatase and rutile is described with a representative octahedron for each phase. The detailed analysis of the atomic bond lengths forming these octahedra helps to understand the macroscopic properties observed in these materials. In rutile samples with an average crystal size between 9.77(9) and
149(2)
nm
, these lengths did not depend on the crystal size. This behavior is not necessarily similar for anatase and brookite, which have crystalline structures with lower symmetry. The dependence of anatase on rutile in synthesis conditions suggests that atom bond lengths in this titanium polymorph depend on crystal size. Brookite is stabilized with copper and chloride ions. Anatase open crystalline structure can dissolve cations and anions that stabilize it at high temperatures, or can be used as precursors for preparing titanates at low temperatures. Rutile, which is normally obtained after annealing brookite and anatase at high temperatures, can be synthesized at low temperatures in the presence of platinum or tin ions during synthesis or by using TiCl
3 as precursor
Effects of Nb doping on the TiO2 anatase-to-rutile phase transition
We study the influence of Nb doping on the TiO2 anatase-to-rutile phase transition, using combined transmission electron microscopy, Raman spectroscopy, x-ray diffraction and selected area electron diffraction analysis. This approach enabled anatase-to-rutile phase transition hindering to be clearly observed for low Nb-doped TiO2 samples. Moreover, there was clear grain growth inhibition in the samples containing Nb. The use of high resolution transmission electron microscopy with our samples provides an innovative perspective compared with previous research on this issue. Our analysis shows that niobium is segregated from the anatase structure before and during the phase transformation, leading to the formation of NbO nanoclusters on the surface of the TiO2 rutile nanoparticles
Effects of Nb doping on the TiO2 anatase-to-rutile phase transition
We study the influence of Nb doping on the TiO2 anatase-to-rutile phase transition, using combined transmission electron microscopy, Raman spectroscopy, x-ray diffraction and selected area electron diffraction analysis. This approach enabled anatase-to-rutile phase transition hindering to be clearly observed for low Nb-doped TiO2 samples. Moreover, there was clear grain growth inhibition in the samples containing Nb. The use of high resolution transmission electron microscopy with our samples provides an innovative perspective compared with previous research on this issue. Our analysis shows that niobium is segregated from the anatase structure before and during the phase transformation, leading to the formation of NbO nanoclusters on the surface of the TiO2 rutile nanoparticles