Green up-conversion luminescence in Yb³⁺-Pr³⁺ co-doped BaRE₂ZnO₅ (RE=Y, Gd)

Yb³⁺ and Pr³⁺ co-doped BaRE₂ZnO ₅ (RE=Y, Gd) up-conversion (UC) phosphors were successfully synthesized by a modified sol-gel method. The processing parameters and optimal concentration of Pr³⁺ and Yb³⁺ were determined. The structures and luminescent properties of samples were characterized by X-ray diffraction (XRD) and photoluminescence spectra (PL). With the excitation of 980 nm laser diode, UC spectra showed five prominent emission bands centered at 484, 514, 546, 656 and 670 nm, which were attributed to the ¹I ₆→³H₄, ³P₁→ ³H₄, ³P₀→³H ₅, ³P₀→³F₂ and ³P₀→³F₃ transitions of Pr ³⁺, respectively. In the light of the pump power dependence, the possible UC mechanism in Yb³⁺ and Pr³⁺ co-doped BaRE ₂ZnO₅ (RE=Y, Gd) was proposed and discussed.