Preparation And Photothermal Properties Of Rare Earth Doped Perovskite Tungstate Fluorescent Materials

Rare earth-doped perovskite-structured tungstates have attracted attention due to their ex-cellent luminescence properties,high stability,attractive structures,and relatively low phonon energy.It has been gradually reported in the fields of light-emitting diodes,plant growth lighting,anti-counterfeiting and light-temperature sensing.Compared to usual temperature mensuration methods,optical temperature measurement has the advantages of high sen-sitivity,fast response and non-contact.Based on perovskite-structured tungstate compounds,this paper modulates photoluminescence properties and optical thermometry capabilities by c-hanging the type and concentration of rare earth ions,doping transition metal ions,excitatio-n wavelength and sample structure.The details are as follows:（1）.A dual-mode optical thermometry technique based on double perovskite structure Sr2CaWO6:Eu³⁺,Dy³⁺phosphor with dual luminescence centers under different wavelength excitation is proposed.Sr2CaWO6:Eu³⁺,Dy³⁺phosphor was prepared through high temperature solid phase method.The structure of the samples and the lattice substitution of dopant ions in the host lattice were analyzed in detail by XRD,Raman spectroscopy and diffuse reflectance spectroscopy,and confirmation that rare earth ions replace Ca²⁺cation sites.The emission spectrum is regulated by changing the doping concentration of Dy³⁺ions to achieve tunable multicolor fluorescence emission.The energy transfer between WO₆^6-,Eu³⁺and Dy³⁺was confirmed by studying the fluorescence lifetime and emission spectrum,and the energy transfer mechanism was analyzed.By studying the dependence of the emission peak intensity of Dy³⁺and Eu³⁺ions on temperature,the optical thermometry based on the fluorescence intensity ratio of Dy³⁺ions(⁴F_9/2→⁶H_15/2)and Eu³⁺ions（⁵D₀→⁷F1）was realized under the excitation of 355 nm.（2）.On the basis of（1）,in order to study the effect of excitation wavelength change on the photo-temperature performance of double perovskite structure Sr2CaWO6:Eu³⁺,Dy³⁺phosphors,a dual-mode optical thermometry technique based on double perovskite structure Sr2CaWO6:Eu³⁺,Dy³⁺phosphors with dual luminescence centers under different wavelength excitations is proposed.Under excitation at 266 nm,the photoluminescence properties,fluorescence lifetime and variable temperature spectra of the samples were investigated.Compared with the excitation at 355nm,the spectral parameters of the sample can be adjusted by changing the excitation wavelength.Optical thermometry based on fluorescence intensity ratio of Dy³⁺ions(⁴F_9/2→⁶H_13/2)and Eu³⁺ions（⁵D₀→⁷F2）under excitation at 266nm,using the fluorescence lifetime of Eu³⁺ion 594nm emission peak as the second optical temperature measurement variable,a dual-mode optical temperature measurement was realized.Compared with excitation at a single wavelength,optical temperature measurement at different wavelengths is conducive to the realization of self-calibration and high-accuracy temperature measurement.The above analysis shows that the Sr2CaWO6:Eu³⁺,Dy³⁺phosphors have the potential to be applied in the field of light and temperature sensing.（3）.A dual-mode optical temperature measurement technology based on CaWO4:Cu⁺,Eu³⁺phosphor with dual luminescence centers is proposed.CaWO4:Cu⁺,Eu³⁺phosphor was prepared through high temperature solid phase method,and the phase structure of the samples was analyzed in detail by XRD and CaWO4 unit cell structure diagram.The photoluminescence properties of the samples were improved by doping transition metal Cu⁺ions.Change the Eu³⁺concentration to tune the emission spectrum.It was confirmed that the dopant ions replaced the Ca²⁺ion sites of the host lattice,and achieved tunable multicolor fluorescence emission.The energy transfer between WO4²-,Cu⁺and Eu³⁺was verified by analyzing the emission spectrum and fluorescence lifetime,and The energy transfer mechanism was analyzed.Transition metal Cu⁺ions are more sensitive to temperature changes than Eu³⁺ions.Through their different dependence on temperature,the optical thermometry based on the fluorescence intensity ratio of Cu⁺ions（³E_g→¹A_g）and Eu³⁺ions（⁵D₀→⁷F₁）under excitation at 266 nm is realized.The fluorescence lifetime of Eu³⁺ion 615nm emission peak is used as the second optical temperature measurement variable,which realizes the dual-mode optical temperature sensing.It shows that CaWO4:Cu⁺,Eu³⁺phosphors are promising in the field of optical temperature measurement.