Preparation Of Rare Earth Doped Calcium Molybdate Luminescent Nano-dispersions By High Gravity Method And Its Application

Nowadays,with the rapid development of various display and lighting technologies,the demand and research on luminescent materials are increasing day by day.Among most of luminescent materials,rare earth doped luminescent materials have attracted much attention due to their advantages such as long life,high color purity and large stokes shift.However,although researchers have prepared rare earth doped luminescent materials through various experimental methods,it is still difficult to synthesize products with controllable size and stable batch due to various reasons.Therefore,in this paper,the high gravity reactor is introduced into the traditional preparation methods,and calcium molybdate up/down-conversion luminescent materials are synthesized in different reaction systems,and the role of the high gravity technology in different reaction systems is studied.The specific research contents are as follows:In the premixed stage of preparing CaMoO4:Yb3+,Er3+upconversion luminescent materials,a high gravity reactor is introduced into the process.In addition,we investigate the effects of the premixed time,high-gravity level and the addition of surfactant on the morphology of the products.As a result,we(?)gravity level is 157 g(corresponding speed is 1500 rpm),and when the dosage of PDDA is 1.5wt%,the product has the best dispersion and the most uniform size(about 800 nm).By comparing with conventional methods,the size of the product is reduced by at least two times.In addition,the application of CaMoO4:Yb3+,Er3+ upconversion luminescent particles in temperature sensing based on FIR technology is also investigated,and we find that the maximum absolute sensitivity SA of the products is 0.02837 K-1 in the temperature range of 300-450 K,which is better than most upconversion luminescent materials reported so far.In the preparation process of CaMoO4 down-conversion nanophosphors,ethanol is used to replace the expensive and toxic organic solvent,and the external circulation reactor is introduced into the premixed stage.The effects of surfactant ratio,solvent ratio,hydrothermal temperature,hydrothermal time,and doping concentration of rare earth ions(Eu3+,Tb3+,Dy3+)on the luminescence properties of the products are also investigated.The results show that the introduction of external circulation reactor and the elimination of organic solvents promote the uniform distribution of rare earth ions and the improvement of crystallinity of calcium molybdate materials.Under the optimal conditions,the high gravity level is 279 g,the surfactant ratio is 1:1,the water-ethanol ratio is 4:9,the doping concentrations of Eu3+,Tb3+and Dy3+are 4%,5%and 1%,and the hydrothermal time and temperature are 2h and 140?,respectively.Panchromatic emission of nano-phosphors in solution and flexible film can be achieved by changing the material ratio of CaMoO4@Sal,CaMoO4:Eu3+,Na+,CaMoO4:Tb3+,Na+,which makes the prepared luminescent materials have a certain potential in w-LED solid-state lighting and flexible display.