Synthesis And Photoluminescence Properties Of Rare Erath Ions Doped Tungstate Phosphors

Recently,the luminescent materials doped with rare earth have been applied to many fields,such as laser anti-counterfeiting,solid state laser,3D display,biological fluorescent probe,solar cell and so on,so that these materials become a hot spot of research.The choice of substrate plays an important role in luminescent materials,tungstate is an important inorganic matrix material,it has many advantages such as low phonon energy,high reflectivity,good stability and simple synthesis process.In this paper,we choose tungstate as the matrix material.Specific contents are as follows:Ca_0.5Gd?WO₄?₂:Er³⁺/Yb³⁺ and Ca_0.5Gd?WO₄?₂:Ho³⁺/Yb³⁺ have been successfully prepared via the high temperature solid state reaction.XRD data shows that the synthesized samples were pure and SEM test shows that all of the samples were spherical shape,the uniform size is 1?m.Under 980 nm light excitation,with the increasing of Yb³⁺ doping concentration,the emission intensity in the visible and near-infrared region of Ca_0.5Gd?WO₄?₂:Er³⁺/Yb³⁺ increases first and then decreases,meanwhile the phenomenon of concentration quenching occurs,the green light and red light in the visible region of Ca_0.5Gd?WO₄?₂:Ho³⁺/Yb³⁺ increases,while the weak blue light shows a stable trend.Under377 nm light excitation,with the increasing of Yb³⁺ doping concentration,the emission intensity in the visible region of Ca_0.5Gd?WO₄?₂:Er³⁺/Yb³⁺ and Ca_0.5Gd?WO₄?₂:Ho³⁺/Yb³⁺ all increases first and then decreases,the emission intensity in the near-infrared region of Ca_0.5Gd?WO₄?₂:Er³⁺/Yb³⁺ increases first and then decreases,meanwhile the emission intensity in the near-infrared region of Ca_0.5Gd?WO₄?₂:Ho³⁺/Yb³⁺ decreases.According to fluorescence decay curves,we calculate the maximum energy transfer efficiency of Ca_0.5Gd?WO₄?₂:Er³⁺/Yb³⁺ and Ca_0.5Gd?WO₄?₂:Ho³⁺/Yb³⁺ is 50.42% and 42.47% respectively,the quantum efficiency is 150.42% and 142.47% respectively.NaGd?WO₄?₂:Er³⁺/Yb³⁺ have been successfully prepared via the hydrothermal method,XRD data shows that the synthesized samples were pure and SEM test shows that when glycol is used as the complexing agent,the sample is cambiform with the smooth surface and few defects.Under 980 nm light excitation,with the increasing of Yb³⁺ doping concentration,the emission intensity in the visible and near-infrared region of NaGd?WO₄?₂:Er³⁺/Yb³⁺increases first and then decreases,meanwhile the phenomenon of concentration quenching occurs.Under 377 nm light excitation,with the increasing of Yb³⁺ doping concentration,the emission intensity in the visible region decreases,the emission intensity in the near-infrared region of 900-1200 nm increases first and then decreases,the emission intensity in the near-infrared region of 1400-1700 nm decreases.According to fluorescence decay curves,we calculate the maximum energy transfer efficiency and quantum efficiency,which is 47.40%and 147.40% respectively.Under 980 nm light excitation,the upconversion fluorescence spectrum of NaGd?WO₄?₂:2Er³⁺/5Yb³⁺ were tested under the temperature of 313K-573 K.The fluorescence intensity ratio of the sample was calculated and analyzed,it is FIR=21.18exp?-996.28/T?according to this,changes of the temperature can be analyzed.we calculate the maximum relative sensitivity of the sample is 0.01145K-1 when the temperature is 498 K.In addition,we also tested and analyzed the near-infrared luminescence intensity of the sample with the increasing of temperature decreases.The result shows that the sample of NaGd?WO₄?₂:Er³⁺/Yb³⁺ have a great potential to use green upconversion region for temperature measurement,at the same time,we also need to pay more attention to the near-infrared region for temperature measurement in the future.