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Compounds with perovskite structures (ABO3), particularly PbTiO3 (PT), in the crystalline form display a semiconductor behavior with a band gap of approximately 3 eV. In the amorphous form, these materials present photoluminescence emission in the region of the visible at ambient temperature, when prepared by the Pechini method. In this way it was decided to investigate an alternative method to obtain nanostructured PT, starting from crystalline PT, with photoluminescence emission in the region of the visible at room temperature. This nanostructure can be obtained by high energy mechanical milling. The high energy mechanical milling process was accomplished in a mechanical mill of the attritor type. The structural and microstructural evolution of the amorphization as a function of the time of milling was followed by X-ray difraction and transmission electronic microscopy. The decrease of the crystallite size was confirmed the broadening of the peaks in the patterns of X-ray difraction. The phenomenon of photoluminescence of the milled powders was accompanied by the Raman sccatering and by techniques of optical absorption (photoluminescence and UV-visible). The results showed that the used process modifies the surface of the particles, leading to a highly disordered state. The high degree of structural disorder is sufficient to generate many electronic states located within the energy gap. This ends up in a radiative decline of electronic transitions, that possibly should be responsible for the photoluminescence. Besides, it was verified that the efficiency of the milling process increases when are used spheres with reduced size, because the contact area between the surfaces of the spheres and the samples increases. This suggests that the amorphization process is preferentially provoked by shear.

Caracterização óptica e estrutural de PbTiO3 nanoestruturado obtido por moagem mecânica de alta energia.