Preparation Of Trivalent Rare Earth Doped BaY₂O₄,LiYGeO₄ Long Persistent Luminescence Materials And Research On Their Luminescent Properties

With the development of inorganic persistent luminescence materials,they have been extensive used in all aspects of life.The progress of science and technology has broadened people's application fields in materials,and puts forward higher requirements for the performance of long persistent luminescence materials.In practical application scenarios,long persistent luminescence materials still have some shortcomings,especially the red persistent luminescence materials located in the long wavelength range,as one of the three primary persistent luminescence materials,because of the insufficient luminescent properties and chemical stability of the commonly used red persistent luminescence materials,the further application of long persistent luminescence material system is affected.Therefore,in view of these problems,it is of great practical significance to explore and study new red persistent luminescence materials.This paper is divided into four chapters,exploring new ideas and new materials for designing and synthesizing new red persistent luminescence materials from two aspects:the matrix structure suitable for forming the luminescence center of the activated ion and the activator ion suitable for the luminescence wavelength.The first chapter systematically elaborates the development history,research progress,common classification,afterglow mechanism models and common preparation methods of long persistent luminescence materials,and clarifies the research background and significance of this paper.The second chapter mainly introduces the preparation materials,equipment,preparation methods,testing and characterization methods.In the third and fourth chapters,the research work and results of this thesis are described completely.The main research contents are summarized as follows:(1)BaY₂O₄:Dy³⁺phosphors were synthesized using the solid-state method.X-ray diffraction,photoluminescence,persistent luminescence,and thermo-luminescence spectra were employed to characterize the phosphors.The powder X-ray diffraction pattern confirms its orthorhombic structure.Photoluminescence emission and excitation spectra were investigated as a function of Dy³⁺ion concentration.The photoluminescence excitation spectra revealed that the Dy³⁺excitation band has a main excitation center located at 351 nm.The photoluminescence spectra exhibits an intense yellow emission due to a strong ⁴F_9/2?⁶H_13/2transition at 578 nm,a weak ⁴F_9/2?⁶H_15/2 transition at 488 nm,and a feeble ⁴F_9/2?⁶H_11/2transition at 670 nm.According to the characteristic emission(⁴F_9/2?⁶H_J),the concentration of Dy³⁺ions was optimized to 1 mol%.The trap depths were examined by the thermo-luminescence glow curves.In addition,in the process of exploring the persistent luminescence and thermo-luminescence mechanism of BaY₂O₄:Dy³⁺phosphors,doped Dy³⁺was found to form defects and act as charge carrier traps,resulting in 60 minutes persistent luminescence.(2)A new red persistent luminescence(Per L)material LiYGeO₄:Eu³⁺has been developed.The experimental results show that the LiYGeO₄:Eu³⁺material with low doping concentration can emit high-intensity red Per L,which can last for much more than 21 hours.The red Per L of the pre-irradiated LiYGeO₄:Eu³⁺phosphor can be repeatedly excited to increase the intensity by short-term stimulation with low-energy near-infrared(NIR)light.Besides,the material can produce strong intrinsic emission and prove to be effective in enhancing the f-f emission of Eu³⁺.Per L emission spectrum,photoluminescence emission spectrum,and thermo-luminescence spectrum are identical,indicating that the emission originates from the host and Eu³⁺emission center.At the same time,thermo-luminescence experiments were carried out,and the characters of traps were intensively studied by the Booth-Bohun method and T_m-T_stop method.The results reveal the Per L mechanism and the important role of Eu³⁺as the introduced traps.This Per L material can greatly enhance the application value of the red Per L material.Besides,LiYGeO₄:Eu³⁺material with high doping concentration shows excellent photoluminescence properties and thermal stability,and its quantum efficiency far exceeds that of commercial phosphors(Y₂O₃:Eu³⁺),which makes the material has potential application value in the field of solid-state lighting.These results show that the material can be used to achieve different luminescence properties through low doping and high doping.