Upconversion luminescence properties and mechanism of Er³⁺ doped Ba_0.65Sr_0.35TiO₃ ferroelectric oxide nanocrystals

Abstract

Ba_0.65Sr_0.35TiO₃ (BST) nanocrystals doped with different concentrations of Er³⁺ ion were fabricated using sol-gel method. The structure and morphology of these BST nanocrystals were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The X-ray diffraction patterns of all the nanocrystals prepared in the study correspond to polycrystalline perovskite BST structure. The blue and green upconversion luminescence properties of Er³⁺ doped BST nanocrystals were investigated under excitation by a 785-nm laser. The upconversion emission bands centered at 407, 523, and 547 nm can be attributed to ²H_9/2, ⁴I_15/2, ²H_11/2, ⁴I_15/2, and ⁴S_3/2, ⁴I_15/2 transitions of Er³⁺ ion, respectively. The upconversion mechanism was studied in detail, based on the laser power dependence of the upconverted emissions. In addition, we examined the dependence of the intensity of green upconverted luminescence on the doping concentration of Er³⁺ ions, and discussed the mechanism underlying the process.

Keywords

Er³⁺: BST nanocrystals / upconvension / luminescence / quenching

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