Upconversion Luminescence Characteristics And Temperatyre Sensing Of Rare Earth Doped Sodium Gadolinium Molybdate Phosphors

In recent years,researchers pay more and more attention to the application of rare earth up-conversion luminescence materials in lighting,sensing,biological imaging and so on.Due to the rich energy level structure of rare earth elements,it can produce visible light emission in a wide range of color gamut.Therefore,the application of rare earth up conversion materials in LED to achieve warm white light emission is a more important research direction.In the study of temperature sensing of rare earth materials,fluorescence intensity ratio temperature measurement technology based on thermal coupling energy level is a common technology.Many kinds of matrix materials can achieve fluorescence intensity ratio temperature measurement,but different materials have different sensitivity,temperature range and precision.Therefore,the study of temperature measurement sensitivity is of great value.The main contents of this paper are as follows.Firstly,Er/Yb co-doped NaGd(MoO₄)₂materials were prepared by sol-gel method.The luminescence intensity of the materials was optimized by controlling the concentration of sensitizer ions,the concentration of activator ions,the concentration of citric acid and the calcination temperature,respectively.For the samples with the strongest luminescence,the concentration of Er is 1%,the concentration of Yb is 24%,the concentration of citric acid is three times that of trivalent metal ions,and the calcination temperature is 800?.Combined with XRD,SEM and fluorescence spectrum at 980 nm,the effect of ion doping on up-conversion luminescence was analyzed.And the up-conversion luminescence characteristics of the materials were explained from the perspective of energy transfer.Then,the luminescence spectra of Er³⁺/Yb³⁺co-doped NaGd(MoO₄)₂phosphors were measured from room temperature to about 500 K by controlling the concentration of sensitizer,activator and calcination temperature.Furthermore,the temperature measurement curves of different doped upconversion materials are obtained.Then,the temperature measurement sensitivity of the materials is obtained.It is found that the temperature sensitivity changes regularly with the change of Er³⁺doping concentration,Yb³⁺doping concentration and calcination temperature.Combined with the upconversion energy level diagram and rate equation,this phenomenon is explained and guessed.It is found that the maximum temperature sensitivity of the material is 28%for Yb³⁺and 0.5%for Er³⁺.The calcination temperature of the sample is 1000?.The results show that the Er³⁺,Yb³⁺co-doped NaGd(MoO₄)₂phosphor is an excellent temperature sensing material.Finally,NaGd(MoO₄)₂:Yb³⁺/Tm³⁺/Er³⁺and NaGd(MoO₄)₂:Yb³⁺/Tm³⁺/Ho³⁺were prepared by sol-gel method,respectivily.The white upconversion luminescence of two kinds of three-doped materials was realized by different rare earth ion doping ratio and excitation power.NaGd(MoO₄)₂:Yb³⁺/Tm³⁺and NaGd(MoO₄)₂:Yb³⁺/Ho³⁺were prepared by sol-gel method.The white light was obtained by physicaly mixing the two co-doped up-conversion materials by a simple grinding method.The luminescence mechanism and characteristics of three kinds of white light materials were analyzed and compared.Through the process of energy transfer and photon transfer,combined with the preparation process and other conditions,the advantages and disadvantages of three kinds of white light up-conversion materials are explained,which provides a new idea and method for the preparation and research of rare earth molybdate up-conversion white light materials in the future.