Investigation On Multicolor Fluorescence Properties Of Rare Earth Doped Fluorophosphate Phosphors

At present,the method of obtaining white LED is mainly composed of blue InGaN LED chip and YAG:Ce³⁺yellow phosphor with garnet structure.However,due to the absence of red component in the spectrum,the color rendering index of white LED is low?R_a<80?.To solve the above problems and obtain high-quality white LED,people use the combination of green and red fluorescent powder to replace the single YAG:Ce³⁺yellow fluorescent powder.This scheme can effectively compensate the missing red component of the device,but due to the reabsorption problem between different phosphors,the luminous efficiency of the device is reduced.Therefore,the realization of single substrate high color rendering white LED phosphor has become a research hotspot in this field.In this paper,Sr₃YNa?PO₄?₃F?SYNPF?was selected as the matrix by high temperature solid-state method,and different rare earth ions were added to realize the continuous color adjustment of phosphor.The crystal structure,energy transfer between ions,luminescent properties,thermal stability and other properties of the samples were systematically studied.?1?SYNPF phosphors with different concentration of Tb³⁺were synthesized by high temperature solid state method.The structure,luminescent properties and thermal stability of the samples were studied by means of X-ray diffraction,excitation emission spectrum and fluorescence decay.The critical distance of energy transfer between Tb³⁺in SYNPF was obtained by using emission spectrum,fluorescence decay spectrum,Dexter theory and I-H model.In addition,we also studied the thermal stability of the sample,which showed the best thermal stability at the doping concentration of 0.3 mol.Under the normal working temperature of LED?150°C?,the luminous intensity of the sample was still as high as 92%at room temperature.?2?SYNPF series samples with different Ce³⁺and Tb³⁺concentrations were synthesized by high temperature solid state method.The blue?0.220,0.10670?green?0.2885,0.5423?light conversion of the sample was realized by the energy transfer between Ce³⁺and Tb³⁺.With the increase of Tb³⁺concentration,the energy transfer efficiency between Ce³⁺and Tb³⁺increased gradually.When the doping concentration of Tb³⁺was 0.5 mol,it reached the maximum value?81.6%?.The critical distance of energy transfer between Ce³⁺and Tb³⁺is calculated to be9.54?by analyzing the excitation emission spectrum and fluorescence decay spectrum of the sample,which shows that the energy transfer mechanism between Ce³⁺and Tb³⁺is the interaction between electric dipole and electric quadrupole.In addition,the thermal stability of the phosphor was studied systematically.At 150°C,the luminescent properties of the sample showed good stability?59.36%of the room temperature value?.?3?SYNPF series samples doped with Ce³⁺and Mn²⁺were synthesized by high temperature solid state method.The blue?0.220,0.10670?yellow?0.4377,0.5213?light conversion was realized by the energy transfer between Ce³⁺and Mn²⁺.The energy transfer efficiency between Ce³⁺and Mn²⁺increased gradually,and reached the maximum value?69.3%?when the concentration of Mn²⁺was 0.2 mol.Through the analysis of excitation emission spectrum and fluorescence decay spectrum,the critical distance of energy transfer between Ce³⁺and Mn²⁺in the sample is 10.92?,which shows that the energy transfer mechanism between Ce³⁺and Mn²⁺is the interaction between electric dipole and electric quadrupole.We studied the thermal stability of the phosphor and found that the luminescent intensity of the sample was 58.02%of the room temperature value at 150?.