Titanium dioxide has attracted much attention since a long time ago due to its versatility as advanced material. However, its performance as semiconductor devices is very much dependent on the predominant crystalline phase and defect concentrations, which can be adjusted through the synthesis methods, thermal treatments and doping processes. In this work, an accurate structural characterization of titanium dioxide was used by X-ray diffractometry supported by rietveld refinement and thermal analysis. The insertion of 5 mol% of zirconium silicate was able to stabilize anatase up to 900 C, permitting the oxygen vacancies to be significantly eliminated. It was demonstrated also that the changes in the isotropic thermal parameters for oxygen are related to reconstructive transformation necessary to promote the anatase-to-rutile phase transition. Independently of doping process, the crystallization process of anatase phase as a function of temperature increasing occurs exclusively due the reduction of lattice microstrain up to 600 C. However, above 650 C, that crystallization process becomes dependent of the increasing in crystallite size. The anatase crystallite growth event was only possible when the titanium dioxide was doped with zirconium silicate. Otherwise, the rutile phase amount starts to rise continually. Thus, there are optimistic expectations for that new composition to be a new semiconductor matrix for additional doping processes.

The anatase phase of titanium dioxide ceramic material plays important rule in heterogeneous photocatalysis, beside the global phase amount and powder morphology. Some of structural parameters are useful to predict several properties, including the crystallization process and mechanism of the irreversible anatase-to-rutile phase transition. The photocatalytic process is based on charge transference from electron-hole pair to material surface, starting some redox reactions in aqueous media. The stable positive defects harm the recombination event and improve the final properties of that material. Modifiers with lower oxidation state than titanium (IV) is applicable for this purpose, what idea becomes the objective of this work. The Sol-Gel method was used to prepare bare and zinc doped-titanium dioxide powder samples reaching good compositional homogeneity for both samples calcined at 500 oC for 4 hours. Rietveld refinement carried out from raw x-ray diffraction patterns was used to demonstrate the formation of solid solution between zinc and titanium oxides. Besides that result, the determination of bandgap energy and SEM images corroborated the structural changes caused by zinc insertion in anatase phase and important difference in powder morphology was observed for zinc doped powder samples in order to reduce the agglomeration degree for better performance for heterogeneous photocatalysis applications.

No presente trabalho catalisadores de TiO2 foram preparados pelo método solgel e incorporados em membranas de borracha natural nas quantidades de 0, 5, 10 e 15% (massa/massa). Os materiais obtidos foram caracterizados por difratometria de raios-X (DRX), microscopia eletrônica de varredura (MEV), termogravimetria (TG-DTG) e calorimetria exploratória diferencial (DSC). A partir das técnicas utilizadas foi possível avaliar que o material cerâmico se apresenta na fase anatase e não influencia na estabilidade térmica da borracha, que permanece com temperatura T0 próxima a 300 °C. A temperatura de transição vítrea da borracha também não é alterada pelo TiO2, permanecendo próxima a-63 °C. As características físicas e químicas bem como a morfologia das membranas obtidas, evidenciam que a borracha natural crua se mostra interessante para tal aplicação.

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