Spectroscopic signature of pyrochlore erbium titanate nanocrystals precipitated in high phonon silicate matrix

Author(s): H C Vasconcelos

Several rare-earth doped optical materials have been developed for photonic applications, mainly for applications such as semiconductor lasers (or diodes), fl uorescent labels and optical amplifi ers. In particular, erbium ions (Er3+) doped SiO2 sol-gel glasses have attracted increasing importance as amplifi er devices. The incorporation of TiO2 into the SiO2 glass, as a structural modifi er, is a suitable strategy to reduce the high phonon energy of asymmetrical Si-O-Si stretching vibrations (~1080- 1100 cm-1) in the SiO2 glass, while that of the Si-O-Ti bonds is comparatively lower (~ 920-960 cm-1). TiO2 co-doping create – (Si-OTi)– bonds in the glass structure, as demonstrated by the FTIR spectrum. On the other hand, during the annealing process, ETO Nano crystallites can be single precipitated in the main matrix for specifi c conditions (depending on Er3+ content, temperature and time of heat treatment) as revelled by XRD. Er3+ ions are thus divided between the host glass and the nano crystallites. This ordered (crystalline) environment would avoid undesired Er3+ ions clustering. In a previous work, it was revealed that Er3+ ions within SiO2 -TiO2 sol-gel glasses are inserted in nanocrystals of pyrochlore erbium titanate, Er2 Ti2 O7 (ETO). Additionally, a pure Er2 Ti2 O7 pyrochlore based waveguide was obtained with remarkable spectroscopic properties and reduced non-radiative absorption mechanisms. However, no signature of such phase considering it spectroscopic characteristics in host glasses was reported yet. In this work, an optical spectroscopic analysis of ETO in transparent SiO2 -TiO2 glass–ceramics is presented.