Structural and Spectroscopic Properties of Luminescent Er ³⁺ ‐Doped SiO ₂ –Ta ₂ O ₅ Nanocomposites

Abstract

This paper reports on the preparation and structural, morphological, and luminescence properties of Er 3+ ‐doped nanocomposites based on SiO 2 –Ta 2 O 5 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°C for formation of the xerogel, followed by annealing at 900°, 1000°, and 1100°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. Er 3+ emission in the infrared region, assigned to the 4 I 13/2 → 4 I 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 Er 3+ ions are preferentially localized close to the region rich in Ta 2 O 5 nanoparticles. The localization of Er 3+ ions was shown to be dependent on the amount of tantalum. Moreover, the fact that the Er 3+ ions are located close to Ta 2 O 5 nanoparticles promotes a broadband emission with full‐width at half‐maximum of 90 nm around 1550 nm.