Sol–gel Synthesis and Upconversion Luminescent Properties of Yb³⁺,Er³⁺,Eu³⁺ Triply-Doped in YVO₄ Phosphors

Abstract

Yb³⁺,Er³⁺,Eu³⁺ triply-doped in YVO₄ with varying molar ratio of Er/Eu were synthesized in a sol–gel method with a subsequent heat treatment for the first time. The optimal molar ratio of Er/Eu for the maximum energy transfer efficiency was 1/39. After molar ratio, the influences of different heat treatment temperatures were also researched and the maximal heat temperature was 1300 °C. Besides, the properties of YVO₄:Yb³⁺,Er³⁺,Eu³⁺ upconversion phosphors were investigated by X-ray diffraction, scanning electron microscopy and photo luminescent spectra, respectively. In sum, XRD results indicate the crystal structure of as-prepared samples, which is the tetragonal phase of YVO₄ with no other diffraction peaks. SEM images show the morphology of as-prepared samples, which are granular-like nanoparticles. PL spectra demonstrate the upconversion luminescence of as-prepared samples, which emit strong green lights (at 525 nm, 550 nm) and slight red lights (at 590 nm, 615 nm, 695 nm) under the NIR irradiation at 980 nm. Two strong green emissions are attributed to the ²H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2 transitions of Er³⁺ ions. Meanwhile, three slight red emissions are attributed to the ⁵D₀→⁷F₁, ⁵D₀→⁷F₂ and ⁵D₀→⁷F₄ transitions of Eu³⁺ ions. All in all, the colorful emissions endow YVO₄:Yb³⁺,Er³⁺,Eu³⁺ phosphors great potential for some applications, such as display devices, bio-labeling and infrared detection.