The Synthesize And Temperature Sensing Research On Yttrium Vanadate Luminescent Materials

Rare-earth doped luminescent materials have the advantages of non-contact,high resolution,fast response,and wide application range in the field of temperature detection,and have become the focus of research in recent years.Many rare earth doped luminescent materials have been studied as temperature sensors at present,but it has been the direction of many scientific researchers to achieve accurate temperature measurement and improve temperature measurement sensitivity.In this paper,yttrium vanadate?YVO₄?was used as a matrix,and Eu³⁺,Pr³⁺,Er³⁺,and Yb³⁺rare earth ions with similar radii to Y³⁺were selected.The prepared samples were characterized by XRD,SEM and luminescence characteristics.The effect of doping concentration on the structure and luminescence characteristics of yttrium vanadate phase was studied,and the temperature sensing characteristics of the samples were studied based on the fluorescence intensity ratio technique.The specific research content is as follows:Eu³⁺ion-doped YVO₄ phosphor was prepared by hydrothermal method,and its structure and morphology were characterized by XRD and SEM.XRD results showed that the doping of Eu³⁺ ions at different concentrations did not change the YVO₄ phase structure.SEM showed that the prepared phosphors were irregular particles with non-uniform size,and the maximum particle size could reach 4 ?m.Under the excitation of 398nm,the emission peak of the sample is mainly concentrated in the visible light range,and the optimal doping concentration is 8%Eu³⁺.In the temperature measurement range of 303K-623K,the peak intensity of the luminous peaks in the temperature-varying spectrum showed a temperature dependence.Based on the fluorescence intensity ratio techniques of thermally coupled energy levels?5D1?7F1 and 5D0?7F1?and Stark energy levels?5D0?7F2?1?,?2?and 5D0?7F4?1?,?2??,the temperature sensing characteristics of YVO₄:Eu³⁺were studied.The results show that the temperature-sensing sensitivity Sr=2.7%K^-1@303K based on the thermal coupling energy level is better than the temperature-sensing sensitivity Sr=0.0956%K^-1@303K based on the Stark energy level.YVO₄:Pr³⁺phosphor was prepared by high-temperature solid-phase method.XRD results showed that the incorporation of Pr³⁺ions did not change the crystal structure of YVO₄.Due to the macro-residual stress in the grain growth caused by the high temperature treatment process,the lattice distortion is caused,and the unit cell volume becomes smaller.SEM results showed that the prepared YVO₄:Pr³⁺ sample was composed of irregular particles with an average particle size of about 3 ?m.Under the excitation of 325nm,the emission spectrum of YVO₄:Pr³⁺phosphor shows the characteristic luminescence of rare earth Pr³⁺ ions,of which 595nm and 598nm belong to the excited state 3p1?3H6 energy level transition,and the corresponding energy level transitions at 605nm and 607nm are 1D2?3H4,and the emission peak at 618nm corresponds to the 3P0?3H6 energy level jump of the rare earth Pr³⁺ ion.Using the fluorescence intensity ratio technology,the temperature sensing characteristics of the sample's YVO₄:Pr³⁺ were studied based on thermally coupled energy levels?3P1 and 3P0?,non-thermally coupled energy levels?3P0 and 1D2?,and 1D2 energy levels:0.783%K^-1@303K,1.137%K^-1@313K,0.398%K^-1@323K?Er³⁺single-doped and Er³⁺/Yb³⁺co-doped YVO₄ phosphors were prepared by a high-temperature solid-phase method.XRD results showed that the single-doped and double-doped products both maintained the matrix YVO₄ crystal structure and no heterophase appeared.The SEM results showed that the surface of Er³⁺/Yb³⁺double-doped YVO₄ phosphor particles was smooth and the average particle diameter was about 1-2 ?m.The down-conversion luminescence peaks of YVO₄:Er³⁺and YVO₄:Er³⁺/Yb³⁺phosphors are mainly green,and the incorporation of Yb³⁺ions enhances the luminescence of Er³⁺ions,indicating that Yb³⁺ions have a good sensitizing effect on Er³⁺ions.The up-conversion luminescence and down-conversion luminescence characteristics of Er³⁺/Yb³⁺double-doped YVO₄ samples were studied under 380nm and 980nm excitation,respectively.In the down-conversion luminescence,the green luminescence of the sample at 526nm?2H11/2?4I15/2?is significantly higher than that of 554nm?4S3/2?4I15/2?green luminescence,which is opposite to the phenomenon under 980nm excitation.Based on the thermal coupling energy level?2H11/2 4I15/2 and 4S3/2?4I15/2?fluorescence intensity ratio technology,the temperature sensing characteristics of Er³⁺/Yb³⁺double doped YVO₄ phosphors were studied.In the 303K-603K temperature measurement interval,the maximum temperature sensitivity obtained when the up-conversion and down-conversion light emission were based on the thermal coupling energy levels?2H11/2 and 4S3/2?was Sr=0.922%K^-1?303K,Sr=0.997%K^-1@303K,respectively.Based on the Stark level?4S3/2?1??2?4I15/2,4I13/2?,the maximum temperature-sensing sensitivity obtained at 303K during down conversion is Sr=0.175%K^-1,Sr=0.158%K^-1.