Preparation,Structure And Luminescence Properties Of Eu³⁺/Sm³⁺/Dy³⁺ Doped Calcium Molybdate Phosphors

Molybdate is an important inorganic chemistry material.It has excellent optical and structural characteristics such as wide emission spectrum,high refraction,high color purity index,strong charge transfer between 2p(O^2-)and 4d(Mo⁶⁺)orbits.Moreover,it is inexpensive,easy to synthesize,and environmentally friendly,making it an inorganic fluorescent material with broad application prospects.Molybdate has attracted the attention of researchers due to its excellent properties.Eu³⁺,Dy³⁺,Sm³⁺ are important luminescence centers in luminescence materials.Therefore,in this paper,CaMoO₄ is selected as the substrate,and Eu³⁺/Dy³⁺/Sm³⁺ is used as the luminescence center.A series of phosphors were prepared by a mild hydrothermal method,characterized and analyzed by X-ray diffraction,infrared spectroscopy,fluorescence spectroscopy to explore their luminescence properties and energy transfer mechanism.This study prepared CaMoO₄:Eu³⁺/Sm³⁺ phosphors.The XRD results showed that the sample is a tetragonal CaMoO₄ phase,the space group is I41/a（88）,the lattice constant are a = b = 5.226 ?,c = 11.430 ?,and V =31.2 ?³.The optimal temperature for the preparation of phosphor is 180 ℃,the optimal reaction time is 24 h,and the optimal doping content of Eu³⁺ is 7%.The existence of O^2-→Mo⁶⁺,O^2-→Ca²⁺ migration bands in the excitation spectra of CaMoO₄:Eu³⁺phosphors at 200 350 nm was confirmed by gaussian fit.Under excited at 283 nm,CaMoO₄:Eu³⁺phosphors exhibited characteristic emission of Eu³⁺ at ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂,and Eu³⁺ occupied an irreversible center of symmetry in the CaMoO₄ matrix.In the Eu³⁺ and Sm³⁺ co-doped CaMoO₄ phosphors,the introduction of Sm³⁺ enhanced the luminescence intensity of the sample by approximately 35%.The optimal doping amount of Eu³⁺ is 1%.In addition,the Eu³⁺ and Sm³⁺ co-doped in CaMoO₄ have synthesized white phosphors.This study prepared Bi³⁺/WO₄^2-doped CaMoO₄:Eu³⁺ phosphors.Based on the above experiments,the optimal concentration of Eu³⁺ was determined to be 7%.XRD results showed that the introduction of Bi³⁺ did not affect the results of the matrix material,but by changing the MoO₄^2-:WO₄^2-ratio,the diffraction peak position of the sample showed a slight displacement compared to the standard card,which was due to the mutual substitution of W⁶⁺ and Mo⁶⁺.The excitation and emission spectra results indicated that the introduction of Bi³⁺ causes red shift in the broadband region at 300 318 nm,which may be influenced by the transition of O^2-→Bi³⁺ and the self-absorption of Bi³⁺.The introduction of WO₄^2-did not change the position and shape of the excitation and emission peaks.The introduction of Bi³⁺/WO₄^2-effectively improved the luminescence intensity of the sample.The optimal doping amount of Bi³⁺ is 0.2%,and the optimal ratio of MoO₄^2-: WO₄^2-= 2:1.This study prepared Eu³⁺ and Dy³⁺ co-doped CaMoO₄ phosphors.Determine that the total amount of Eu³⁺ and Dy³⁺ is 9%.Under excited at a certain wavelength,CaMoO₄:x Eu³⁺,（9%-x）Dy³⁺ exhibited strong emission peaks for Eu³⁺ at 614 nm（5D0→7F1）and Dy³⁺ at 574 nm（4F9/2→6H13/2）.By adjusting the doping content of Eu³⁺ and Dy³⁺,the phosphor achieved color regulation from green→cold white→warm white→yellow.A series of fluorescent powders were synthesized by introducing monovalent alkali metal Li⁺/Na⁺/K⁺,divalent alkaline earth metal Sr²⁺/Ba²⁺,and trivalent metal La³⁺/Gd³⁺ into the best luminescent powders CaMoO₄:7.5%Eu³⁺,1.5%Dy³⁺.La³⁺/Gd³⁺ entered the matrix lattice results through subsititution,resulting in a small amount of impurity peaks in the XRD diffraction peaks.Except for Ba²⁺,other ions increased the luminescence intensity of the fluorescent powder to varying degrees.