Structural and luminescence properties of Nd3+/Yb3+ codoped Al4B2O9 nanocrystalline powders

Abstract

Morphological, structural and optical properties of Nd³⁺/Yb³⁺ codoped Al₄B₂O₉ nanopowders prepared by the polymeric precursor method were investigated. The compounds previously heat-treated at 900 °C were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) techniques. The Al₄B₂O₉ nanocrystals obtained possess an orthorhombic structure with grain dimensions between 10 and 20 nm. Photoluminescence (PL) spectra under excitation at 804 nm were collected and analyzed. The results indicate that the energy absorbed by Nd³⁺ (transition: ⁴I_9/2 → ⁴F_5/2 + ²H_9/2) is efficiently transferred to Yb³⁺ in samples having 2 mol% of Nd³⁺ and 1 mol% of Yb³⁺, increasing the emission from 930 nm to 1130 nm by 12.2 times in comparison with the samples doped with 1 mol% of Nd³⁺ and 1 mol% of Yb³⁺. The dynamics of the PL process was also investigated. The PL decay at 975 nm from Yb³⁺ (²F_5/2 → ²F_7/2) and at 1080 nm from Nd³⁺ (⁴F_3/2 → ⁴I_11/2) was studied. The Yb^{3+ 2}F_5/2 level lifetime varies from 201 to 48 μs while the lifetime of the Nd^{3+ 4}F_3/2 level varies from 121 to 69 μs when the Nd³⁺ concentration is changed from 1 to 8 mol%. On the other hand, the Yb^{3+ 2}F_5/2 lifetime varies from 176 to 15 μs and the Nd^{3+ 4}F_3/2 lifetime varies from 97 to 44 μs when the Yb³⁺ concentration is changed from 1 to 8 mol%, due to interactions between the rare-earth ions. The present results show that Nd³⁺/Yb³⁺ codoped Al₄B₂O₉ nanocrystalline powders have large potential to be tested in solar energy concentrators and IR laser devices.