Study On Preparation And Properties Of Bi³⁺/Mn⁴⁺ Activated Oxide Fluorescent Materials

Compared with traditional incandescent bulbs and fluorescent lamp technologies,white light sources based on light-emitting diodes(LEDs)have the advantages of high light efficiency,long life,and low energy consumption.Therefore,as a new generation of solid-state lighting technology,people Strong research interest.The most commonly used method for white-emitting LEDs is to combine a blue-emitting(460 nm)In Ga N chip with a yellow fluorescent material.However,the obvious disadvantage of this method is that the color temperature(CCT>7000K)of the white light LED is higher and the color rendering index(Ra<70)is lower due to the lack of the red part.In order to solve these problems,usually by optimizing the packaged phosphor,adding a red phosphor with excellent performance and matching the excitation wavelength of the blue chip,or changing the luminescent material to improve the practicability of the white light LED device.Based on the above reasons,we prepared a series of Bi³⁺and Mn⁴⁺co-doped red phosphors by high-temperature solid-phase method,and studied their structural morphology,optical properties and practical application effects in white LEDs.At the same time,in phosphor-encapsulated high-power LEDs,the traditional epoxy resin encapsulation method has serious problems such as silica gel aging and thermal quenching.In order to further solve the above problems,we have grown Bi³⁺,Mn⁴⁺Codoped red fluorescent single crystal materials with good physical and chemical properties,high thermal conductivity and thermal stability by Czochralski method.There are six chapters in this thesis.The first and second chapters are the research background overview and experimental methods respectively;the third to fifth chapters are the core experimental part of this thesis;the sixth chapter is the summary and prospect of this thesis.The main research content and results of this thesis are as follows:1.Successfully synthesized Bi³⁺/Mn⁴⁺:Sr Ge₄O₉ red phosphor without rare earth doping by high temperature solid phase method.Firstly,the crystal structure was qualitatively studied by X-ray diffraction experiment;secondly,the basic morphological characteristics and element composition of the sample were obtained by scanning,transmission electron microscopy and XPS;the fluorescence spectrum showed that the phosphor can emit under 474 nm excitation 664 nm red light;finally,Mn⁴⁺:Sr Ge₄O₉ and Bi³⁺/Mn⁴⁺:Sr Ge₄O₉ phosphors were used to encapsulate the LED device and its electroluminescence performance was studied.The obtained white LED device has a high lumen efficiency(93.1 lm/W)and good color development(Ra=83.1),which proves that the Bi³⁺/Mn⁴⁺:Sr Ge₄O₉red phosphor is a potential red luminescent material for LEDs.2.A series of new Bi³⁺/Mn⁴⁺:Ba₂Ti Ge₂O₈ red phosphors were synthesized.First,the structure and morphology of the sample were studied using XRD,SEM and TEM technology;then the optimal doping concentration of Bi³⁺was obtained through the fluorescence spectrum of the sample;finally,the LED white light experiment was carried out,and good luminous efficiency(97.83 lm/W)and color rendering(Ra=82.2)were obtained.index.Experiments show that Bi³⁺/Mn⁴⁺:Ba₂Ti Ge₂O₈ phosphor has potential application prospects in the field of white light illumination.3.The Bi³⁺and Mn⁴⁺co-doped Gd_0.1Y_0.9Al O₃ phosphors and fluorescent single crystal samples were prepared and grown by the high-temperature solid-phase method and the Czochralski method,respectively.Firstly,the phase purity of the prepared samples was confirmed using XRD standard patterns,and the luminescence properties of the phosphor samples were systematically studied.The luminescence spectrum showed that the deep red emission peak(716 nm)of Mn⁴⁺:Gd_0.1Y_0.9Al O₃ crystal was attributed to the ²E?⁴A₂ transition of Mn⁴⁺ions,which was effectively excited at 468nm.And based on the phosphor samples,a warm-color LED with good luminescence was prepared.After that,we further studied the optical properties of its fluorescent single crystal host material.In the study of the optical properties of fluorescent single crystals,we found that there is a clear overlap between the emission band of Bi³⁺and the excitation band of Mn⁴⁺,which can indicate that the energy transfer phenomenon from Bi³⁺to Mn⁴⁺has occurred,which can effectively enhance the Mn⁴⁺light intensity.Subsequently,the energy transfer mechanism and energy transfer efficiency between the two doped ions were studied through fluorescence lifetime experiments.Finally,according to the emission spectra of Bi³⁺/Mn⁴⁺:Gd_0.1Y_0.9Al O₃ fluorescent single crystals,good CIE coordinates were obtained.These all indicate that Bi³⁺/Mn⁴⁺:Gd_0.1Y_0.9Al O₃ has good deep red luminescence performance,which also proves that Bi³⁺/Mn⁴⁺co-doped Gd_0.1Y_0.9Al O₃ crystal material has potential application prospects in the field of plant lighting.