Structural and Spectroscopic Properties of Luminescent Er3+-Doped SiO2-Ta2O5 Nanocomposites

Abstract

This paper reports on the preparation and structural, morphological, and luminescence properties of Er3+-doped nanocomposites based on SiO2-Ta2O5 prepared by the sol-gel method. The influence of the tantalum oxide content on the structural and spectroscopic properties was analyzed for Si/Ta molar ratios of 90:10, 80:20, 70:30, 60:40, and 50:50. The sols were kept at 60 degrees C for formation of the xerogel, followed by annealing at 900 degrees, 1000 degrees, and 1100 degrees C for 2 h for production of the nanocomposites. The densification, phase separation, and crystallization processes were monitored through vibrational spectroscopy (FTIR), X-ray diffraction, and high-resolution transmission electron microscopy. Er3+ emission in the infrared region, assigned to the 4I(13/2)-> 4I(15/2) transition, was observed for all the nanocomposites. Evolution from a vitreous-like environment to a crystalline one was identified upon increasing the annealing temperature and tantalum content. According to the results obtained, the Er3+ ions are preferentially localized close to the region rich in Ta2O5 nanoparticles. The localization of Er3+ ions was shown to be dependent on the amount of tantalum. Moreover, the fact that the Er3+ ions are located close to Ta2O5 nanoparticles promotes a broadband emission with full-width at half-maximum of 90 nm around 1550 nm.