Study On Preparation And Application Of (Lu_xGd_1-x)₂O₂S:Er³⁺,Yb³⁺ Up-Conversion Luminescence Materials

Up-conversion materials can convert invisible infrared light into visible light,and emit light with greater energy than the excitation photon by photon addition.This material has application value in many fields such as three-dimensional display,anti-counterfeiting recognition,infrared display imaging,biological detection,up-conversion laser and so on.At present,the research on up-conversion materials focuses on single-wavelength response.For the detection of 980 nm,1064 nm and 1550 nm infrared light widely used in the military and civilian fields,a variety of detection products are often needed.Therefore,in this paper,the formulation design through mechanism research to obtain multi-wavelength response infrared up-conversion luminescence materials.The selection of preparation methods of up-conversion materials will greatly affect the performance of materials.With the continuous development of up-conversion materials,many new preparation methods have emerged for applications in different fields.They have their own advantages and disadvantages.For example,the high-temperature solid-phase method is simple to operate and the grain growth is complete,but there are shortcomings such as slow reaction time and high particle size;the co-precipitation method is safe and efficient,with small particle size,but the crystallinity of the sample is not high.Therefore,in this paper,the process parameter control technology of product performance is determined by studying the change rule of product performance with the fusion process parameters of co-precipitation precursor preparation-high temperature solid phase heat treatment,so as to break through the“fine and bright”preparation process of powder materials.The multi-wavelength response,“fine and bright”infrared up-conversion luminescence materials suitable for device matching applications are obtained,and the application development of the materials is preliminarily studied to obtain portable and efficient multi-wavelength response infrared up-conversion detection plate samples.The specific research contents are as follows:（1）The formulation process of multi-wavelength response components was studied.The luminescence and excitation power curves were tested,and the energy level model of multi-photon absorption up-conversion luminescence mechanism was established,and the physical mechanism of multi-wavelength infrared response up-conversion was clarified.According to the mechanism research,the component formula was designed,and the fixed variable method was used to study the concentration of activated ions and sensitized ions in a wide range.The results show that under the premise of three wavelengths,the best component formula is determined by up-conversion emission spectroscopy and XRD.the Er³⁺ion doping concentration range is 10%-16%,the Er³⁺-Yb³⁺concentration ratio range is 1:1-1:4,and the fluorescence decay rate of the sample increases with the increase of Yb³⁺concentration.Optimization by introducing matrix-regulated ions.The results show that the optimum concentration of Lu³⁺ion is 9mol%by up-conversion emission spectrum analysis under the premise of three wavelengths.The fluorescence decay time of the sample increases first and then decreases with the increase of Lu³⁺ion concentration.（2）The process parameters of coprecipitation-high temperature solid-state reaction method were studied.On the premise of taking into account the three wavelengths,the optimum process conditions of the precursor preparation process were determined by up-conversion emission spectroscopy and XRD analysis.The results show that the p H value of the solution is about 6,oxalic acid is used as the precipitant,the dispersant is PEG1000,and the optimal amount of dispersant PEG1000 is 10w%.The formula and process were optimized by orthogonal experiment.Under the premise of three-wavelength response,the optimal formula parameters of(Lu_0.09Gd_0.91)₂O₂S:Er³⁺,Yb³⁺materials were determined by taking the total luminescence intensity as the standard,n(Er³⁺)=13%,n(Er³⁺:Yb³⁺)=1:2,Ph=6.And verify the rationality of the experiment.Through the comparative analysis of the emission spectrum and XRD spectrum under the excitation of three wavelengths,it is considered that the flux is the most suitable when the flux is Na₂CO₃,and the amount of flux Na₂CO₃ is 10:3.2 is better.It is determined that the burning stage is kept at 1050°C for 3h,and the heat treatment series is kept at 700°C for 1h.Through the study of the variation of process parameters,the“fine and bright”up-conversion luminescence material was successfully prepared.Then a series of optimized performance characterization tests are carried out.Through the study of the up-conversion emission spectrum of the best sample at three wavelengths,under the excitation of 980 nm and 1064 nm,it shows green emission,while under the excitation of 1550 nm,it shows red light enhancement.The XRD pattern analysis and refinement results show that the(Lu_0.09Gd_0.91)₂O₂S:Er³⁺,Yb³⁺sample is hexagonal Gd₂O₂S phase,and the calculated actual cell parameters are smaller than the theoretical cell parameters of Gd₂O₂S.The SEM of the best sample shows that the sample is hexagonal crystal phase and the particle size is about 2μm.The infrared response spectrum shows that the best sample exhibits two broadband spectra in the range of 950-1150 nm and1440-1590 nm under the monitoring of the strongest green peak at 550 nm and the strongest red peak at 670 nm.The infrared response threshold of the best sample under three-wavelength excitation conditions is as low as 1.43 m W/cm² at 980 nm,22.3 m W/cm² at 1064nm,and 1.78 m W/cm² at 1550 nm.（3）The application of multi-wavelength response infrared up-conversion materials was studied by screen printing process.According to different application requirements,three different substrates of ceramic sheet,copper-coated cardboard and stainless steel sheet were used,and CTS computer direct plate-making screen printing and coating process was adopted.It is determined that the best screen printing times of coated paper substrate are 10 times,and the best screen printing times of alumina ceramic sheet and stainless steel sheet are 14 times.The mass ratio of ink and powder is 1:1.5.The amount of diluent is 2 m L.So far,better preparation process parameters of multi-wavelength response infrared up-conversion detection plate were obtained,and detection plate samples with different substrates were prepared.