Synthesis and Characterization of Anatase-Structured Titania Hollow Spheres Doped with Erbium (III)

Using a simple method involving chemical synthesis and calcination, Er-doped anatase hollow spheres (HS) have been obtained. Longer dwell times upon the calcination increase the roughness and thickness of the shells, and also facilitate formation of necks between neighboring HS. Anatase-rutile transformation was observed by FT-Raman for the TiO2-HS calcined at 800 degrees C but this was not observed for the doped samples, which indicates that erbium cations inhibit that phase transition. In addition, sintering occurs at higher temperature and it is possible to note a high difference between the undoped-HS and the Er-doped HS in the sintering behavior and microstructural features. Finally, photoluminescence measurements show several peaks which are assigned to different defects of TiO2-like oxygen vacancies or interstitial Ti3+ and to the emission of erbium cations.