Preparation And Luminescence Properties Of Rare Earth Ions Co-doped Phosphate Phosphors

More and more attention has been attracted on white light-emitting diodes（WLEDs）duo to their high luminous efficiency,low energy cost,long operation lifetime,and environmental protection.In this study,Sr_10（1-x）Cl₂（PO₄）₆: 10xEu²⁺,Ca₉NaZn（PO₄）₇: Eu²⁺/Eu³⁺,Tb³⁺ and Ca_2（1-x）B₂P₂O₁₀: 2xEu²⁺ phosphors were prepared by conventional solid-state method.Their crystal structure,microtopography,photoluminescence properties,thermal sability,decay lifetime were studied.1.A series of blue-emitting Sr_10（1-x）Cl₂（PO₄）₆: 10xEu²⁺（x= 0.01,0.02,0.03,0.04,0.05）phosphors were synthesized by conventional solid-state method.The crystal structures and micro-morphology were characterized by X-ray diffraction（XRD）and field-emission scanning electron microscope（FE-SEM）.Their photoluminescence properties were investigated by excitation and emission spectrum.The optimal concentration of Eu²⁺ ions in Sr_10（1-x）Cl₂（PO₄）₆: 10xEu²⁺ was determined to be x = 0.02.The corresponding concentration quenching mechanism was verified to be a combination of radiation re-adsorption and electric dipole-dipole interactions.Thermal stability of Sr_9.80Cl₂（PO₄）₆: 0.20Eu²⁺ were evaluated by investigating temperature-dependent luminescence properties.The luminescence lifetime of Sr₁₀Cl₂（PO₄）₆: Eu²⁺ at various Eu²⁺-doping concentration and different temperature was analyzed.The activation energy（Ea）for thermal quenching was calculated.All results suggest that Sr₁₀Cl₂（PO₄）₆: Eu²⁺ phosphor is a good candidate as a blue component for application in white light-emitting diodes（WLEDs）.2.Ca₉NaZn（PO₄）₇: Eu²⁺/Eu³⁺,Tb³⁺(CNZP: Eu²⁺/Eu³⁺,Tb³⁺)phosphors were synthesized by high-temperature solid state reaction at 1000 ℃.The photoluminescence properties,doping concentrations and decay lifetime of CNZP: Eu²⁺/Eu³⁺,Tb³⁺ were investigated.Partial reduction of Eu³⁺ to Eu²⁺ occurred due to the larger radius of Eu²⁺ than that of Ca²⁺.Two energy transfer behaviors were detected in CNZP: Eu²⁺/Eu³⁺,Tb³⁺ phosphor,namely from Eu²⁺ to Tb³⁺and from Tb³⁺ to Eu³⁺.The PL spectra of CNZP: Eu²⁺/Eu³⁺,Tb³⁺ were adjusted from red to warm white and finally to yellowish-green by changing the doping ratio of activator ions.The phosphors show good thermal stability.The results show that Ca_9-9x-9yNaZn（PO₄）₇: 9xEu³⁺/Eu²⁺,9yTb³⁺（0.00≤x≤0.010,0.003≤y≤0.018）samples are potential color-tunable phosphors for application in white LEDs.3.A new blue-emitting phosphor Ca₂B₂P₂O₁₀: Eu²⁺ was synthesized by the solid state reaction method at 800℃.The X-ray diffraction（XRD）and scanning electron microscope（SEM）were utilized to characterize the prepared phosphors.The luminescence properties of the phosphor were studied by excitation and emission spectrum.The optimum concentration of Eu²⁺ ions in Ca₂B₂P₂O₁₀ was studied to be 1.0 mol%,and the concentration quenching mechanism was studied in detail.