Preparation,Color-tunable Luminescence And Energy Transfer Of Rare-earth Ions Doped Tungstate Phosphors

White LED is known as the fourth generation lighting source as its small volume,high efficiency and low energy consumption,which shows wide application prospects in the display and efficient lighting market.In order to meet the development demand of phosphor converted white LED,the research of novel phosphors with ultraviolet excitation are imminent.The upconversion phosphors excited by 980 nm have been widely applied not only in LED and laser fields,but also in anti-counterfeiting recognition,biological probe,temperature detection,solar cells and other fields.This paper is devoted to synthesis a new type of single substrate multi-color emitting phosphor with dual-mode luminescence under the ultraviolet excitation and 980 nm NIR radiation,and the energy transfer between rare earth ions is also discussed.A series of NaGd?WO₄?₂:Er³⁺,Tb³⁺green phosphors were synthesized via hydrothermal method.In Er³⁺doped NaGd?WO₄?₂,the sensitization of substrate to Er³⁺was discussed.When 378 nm light was used to stimulate samples,the samples produced green emission,and the quenching concentration of Er³⁺is 0.05.The host sensitization effect has also been researched in NaGd?WO₄?₂:Tb³⁺.Under UV excitation of 265 nm,NaGd?WO₄?₂:Tb³⁺phosphors produced green emission and the quenching concentration of Tb³⁺is 0.07.The possible energy transfer process of Er³⁺to Tb³⁺in NaGd?WO₄?₂:Er³⁺,Tb³⁺phosphors has been analyzed.Under 980 nm laser excitation,these phosphors exhibit green emissions,and the mechanism of up-conversion luminescence is proposed.The emission light color of the phosphors can be adjusted by using different excitation wavelength and the doping concentration of Tb³⁺.NaGd?WO₄?₂:Yb³⁺,Ho³⁺,Eu³⁺phosphors were successfully synthesized via hydrothermal process.Upon 452 nm and 980 nm laser excitation,the NaGd?WO₄?₂:Yb³⁺,Ho³⁺phosphors exhibit strong green emissions.Under 395 nm near UV excitation,NaGd?WO₄?₂:Yb³⁺,Ho³⁺,Eu³⁺phosphors emit green and red light.Upon pumped by 980 nm laser,NaGd?WO₄?₂:Yb³⁺,Ho³⁺,Eu³⁺phosphors obtained the characteristic green emission of Ho³⁺and the characteristic red emission of Eu³⁺via energy transfer in Yb³⁺?Eu³⁺.The NaGd?WO₄?₂:Yb³⁺,Ho³⁺,Eu³⁺phosphors can achieve multi-color luminescence with different wavelength excitation.NaGd?WO₄?₂:Yb³⁺,Tb³⁺phosphors were prepared by hydrothermal method.Under UV excitation?275 nm?,NaGd?WO₄?₂:Yb³⁺,Tb³⁺phosphors obtained green emission.Under980 nm laser excitation,the phosphors realize the green emission of Tb³⁺due to the sensitization of Yb³⁺,and the mechanism of up-conversion luminescence is discussed.NaGd?WO₄?₂:Yb³⁺,Tb³⁺phosphors have realized the tunable light color under different excitation wavelengths.