Upconversion and infrared emission of Er³⁺/Yb³⁺ co-doped SiO<inf>2</inf>-Gd<inf>2</inf>O<inf>3</inf> obtained by sol-gel process

Abstract

This work reports on the preparation of materials based on Yb³⁺/Er³⁺ co-doped SiO<inf>2</inf>-Gd<inf>2</inf>O<inf>3</inf> via sol-gel process. The 0.4mol%of Er³⁺ ions was fixed and the amount of Yb³⁺ ions changed as 1.8, 5 and 9mol%in order to evaluate the photoluminescence properties as a function of the Yb³⁺ ions concentration. The prepared xerogels were heat-treated at 900, 1000 and 1100 °C for 8 h. X-ray diffraction analyses of the heat-treated materials confirmed the formation of the Gd<inf>2</inf>O<inf>3</inf> cubic phase embedded in the SiO<inf>2</inf> host, demonstrating the effective incorporation of RE³⁺ ions in the structure. The Scherrer's equation verified that the sizes of Gd<inf>2</inf>O<inf>3</inf> nanocrystallite are between 31 and 69 nm and directly dependent on the heat-treatment temperature. Under excitation at 980 nm all materials showed upconversion phenomena, and the intensities of the emissions in the green and red regions showed to be directly dependent on power pump of laser, quantity of Yb³⁺ ions and heat-treatment temperature. The materials also showed emission in the infrared region with the maximum around 1530 nm, assigned to the transition of ⁴I<inf>13/2</inf> → ⁴I<inf>15/2</inf> of the Er³⁺ ions, region known as technological C-telecom band used in optical amplification.