Thermal/photochromic Effect Induces WO₃: Yb³⁺, Er³⁺ To Reversibly Regulate The Upconversion Luminescence Properties

Rare earth ion doped luminescent materials have broad application prospects in laser,bioimaging and solid state lighting.The enthusiasm of research on RE doped UC phosphors is further driven in order to modulate the luminescence.Therefore,this work mainly focuses on the mechanism of the thermochromic/photochromic effect of tungsten trioxide on the luminescence regulation of rare earth.It has been proved by experiments that it has wide application prospects in optical switching,optical storage and other fields.The WO3:Yb3+,Er3+ phosphors were prepared at the 400? and 600?sintering temperature,respectively.The mechanism of reversible up-conversion luminescence was investigated.The red glow of the phosphor sintered in air at 400? is caused by oxygen vacancies,and the phosphor sintered at 600? glows yellow.The phosphors were heated in the reducing atmosphere at the corresponding temperature to obtain the non-luminous samples after coloring,which was caused by the reduction of W6+ to W5+.After the colored phosphors were heated and bleached in air at the corresponding temperature,all phosphors regained their luminescence because W5+ was oxidized into W6+.W?3:Yb3+,Er3+ phosphors were heated repeatedly in air and reducing atmosphere,and the sample glowed and quenched alternately.It shows that the material has a bright future in the field of optical switching.WO3:Yb3+,Er3+ and WO2:Yb3+,Er3+ phosphors were prepared in air or reducing atmosphere at 1000?.The adjustable up-conversion luminescence mechanism induced by reversible phase transition of tungsten trioxide was investigated.Under 980 nm irradiation,WO3:Yb3+,Er3+phosphors emit green light,and WO2:Yb3+,Er3+ phosphors do not emit light.This is because the metallicity of tungsten dioxide quenches up-conversion luminescence.By adjusting the different atmospheres at 1000? for many times,the reversible phase transition of the phosphor from tungsten trioxide to tungsten dioxide is achieved,and the purpose of adjusting the luminescence and quenching of rare earth ions is achieved.This indicates that the material has application prospects in the field of optical storage.W03:Yb3+,Er3+ porous ceramics were successfully prepared at sintering temperatures of 400?,500?,600? and 700?,respectively.The mechanism of photochromism adjustment upconversion luminescence of WPO3:Yb3+,Er3+ was investigated.When the power density at 980 nm is higher than 0.54W/cm2,it will cause discoloration of the sample,leading to luminescence quenching.After the experiment,the discoloration of the sample is caused by photoinduced thermochromism.After heat treatment,the sample will reglowing.This paper shows that the material has application prospects in light-switching devices with adjustable color.