Research On The Preparation And Photoluminescent Properties Of Aluminate-based (CaAl₁₂O₁₉) Red Phosphors

Aluminate based red phosphors can be applied in white light emitting diode?WLED?owing to their good chemical stability,thermostability and simple synthesis process.In this paper,the preparation and photoluminescent properties of CaAl₁₂O₁₉:Cr³⁺,CaAl₁₂O₁₉:Mn⁴⁺ and CaAl₁₂O₁₉:Eu³⁺ red phosphors were studied.Specific contents are as follows:?1?Firstly,CaAl₁₂O₁₉:Cr³⁺,CaAl₁₂O₁₉:Mn⁴⁺ and CaAl₁₂O₁₉:Eu³⁺ phosphors were synthesized via high temperature solid state method.Based on the studies of the effect of different content of fluxing agent?H3BO3?on the phase structure and luminescence properties of CaAl₁₂O₁₉:Cr³⁺,it was shown that the optimum doping concentration of H3BO3 was 3 mol.%.By studying the excitation and emission spectra of CaAl₁₂O₁₉:Cr³⁺ and CaAl₁₂O₁₉: Sm³⁺,it was found that Sm³⁺ could enhance the emission intensity of CaAl₁₂O₁₉:Cr³⁺ through an energy transfer process.In addition,it is found that both Sm³⁺ and Ge⁴⁺ could enhance the luminescence intensity of CaAl₁₂O₁₉:Cr³⁺ phosphors and the enhancement mechanism was analyzed.?2?Next,the synthesis and photoluminescent properties of CaAl₁₂O₁₉:Mn⁴⁺ red phosphors were investigated.It is shown from the excitation spectrum that the charge transfer band?CTB?of the prepared phosphor was located at 323 nm,which was ascribed to the charge transfer of Mn⁴⁺?O2-.Subsequently,the author investigated the energy levels of Sm³⁺,Cr³⁺ and Mn⁴⁺ ions in CaAl₁₂O₁₉ and found that doping of Sm³⁺ could not enhance the luminescent intensity of CaAl₁₂O₁₉:Mn⁴⁺ red phosphor obviously.Next,the author investigated the charge compensation effects for Mg²⁺,Ge⁴⁺ and Cl^-doped CaAl₁₂O₁₉:Mn⁴⁺ phosphors and then confirmed the enhancement effect.However,it was also found that doping of charge compensation agent?K+?exhibits no substantial enhancement effect on the luminescence properties of CaAl₁₂O₁₉:Mn4.In addition,the effects of co-doped rare earth ions(Pr³⁺,Nd³⁺,Sm³⁺,Tm³⁺,etc.)on the luminescent properties of CaAl₁₂O₁₉:Mn4 were also studied.At the end of this chapter the author constructed the energy level diagrams of lanthanide RE ions(Ln³⁺)and transition metal ions(Mn⁴⁺,Cr³⁺)in the host of CaAl₁₂O₁₉ by analyzing and summarizing the experimental data in this thesis and related literature reports.Especially,charge transfer processes of RE ions(Ln³⁺)and transition metal ions(Mn⁴⁺,Cr³⁺)were investigated.The corresponding research results can provide a basic theoretical basis for the research of CaAl₁₂O₁₉ based luminescent materials.?3?In the end,the luminescent properties of CaAl₁₂O₁₉:Eu³⁺ phosphors were studied,and the luminescence mechanism of Eu³⁺ was analyzed.By studying on the influence of charge compensation agents?Na⁺,Li⁺,Cl^-?on the luminescence properties of CaAl₁₂O₁₉:Eu³⁺ phosphors,it was found that the doped charge compensation agents can enhance the luminescent properties of the phosphors,and the doped Cl^-has the best ability to enhance the emission intensity of CaAl₁₂O₁₉: Eu³⁺.