Hydrothermal preparation and white up-conversion luminescence of NaGd(WO₄)₂:Yb³⁺/Pr³⁺ microcrystals

NaGd(WO₄)₂:Yb³⁺/Pr³⁺ microcrystals with different doping concentration of Pr³⁺ ions have been synthesized by a facile hydrothermal method followed by a subsequent heat treatment process. The structures, morphologies and up-conversion luminescent properties of the as-prepared NaGd(WO₄)₂:Yb³⁺/Pr³⁺ microcrystals were investigated by X-ray diffraction, scanning electron microscopy and photoluminescence spectra. Under the excitation with a 980 nm diode laser, intense red and blue emissions along with some weak emissions in green and yellow regions were observed. The main emission bands of the samples are assigned to ³P₀ → ³H₄, ¹I₆ + ³P₁ → ³H₅, ³P₀ → ³H₅, ¹I₆ + ³P₁ → ³H₆, ¹D₂ → ³H₄, ³P₀ → ³H₆, ³P₀ → ³F₂, ¹D₂ → ³H₅, ³P₀ → ³F₃, and ³P₀ → ³F₄ transitions of Pr³⁺ ions. Concentration quenching appears as the Pr³⁺ ions doping content up to 0.3 mol%. The International Commission on Illumination (CIE) chromaticity coordinates are close to those of the standard illuminant F3 (0.409, 0.394) which reprents white fluoresence. The as-prepared microcrystals might find potential applications in fields such as phosphor powders, infrared detection and display devices.