Preparation And Luminescent Properties Of Rare-earth Doped Calcium Phosphate Phosphors

Rare-earth doped phosphate phosphor is a very important light-emittingmaterial and widely used in lighting and display devices because of itsseveral advantages, such as：high luminous efficiency, good chemical andthermal stability, cheap etc,. In this work, we prepared rare-earth dopedcalcium phosphate phosphors and studied on its luminescent performance.The main reseaches were showed as follows:（1）We prepared red-emitting Ca₃（PO₄）₂:Eu³⁺phosphor via solid-statereaction.The excitation spectra of the phosphors consisted of CTB ofEu³⁺-O^2-and f-f transition of Eu³⁺. The peak at394nm with the maximumexcitation intensity corresponded to7F50â†'L6transition of Eu³⁺. The peak at613nm with the maximum emission intensity was assigned to⁵D₀â†'⁷F₂transition of Eu³⁺. The optimal Eu³⁺doping concentration was10%compared with Ca²⁺. To improve the luminescent intensity, we incorporatedNa+as a charge compensator into the phosphor. The optimal composition ofthe phosphor was confirmed as Ca_2.3Na_0.4（PO₄）₂:0.3Eu³⁺.It was found thatthe red emission intensity of charge compensated phosphor was about2.9times of that of the phosphor without charge compensation.The mechanismabout charge compensation was analyzed in light of defect formation andreaction, and the changes of the site centrosymmetry for activator.（2） We prepared blue-emitting Ca3（PO₄）₂:Eu²⁺phosphor under reducingatmosphere of N^2-H₂via solid-state reaction. The excitation spectracorresponding to4f-5d transition of Eu²⁺showed a broad band between250and400nm and peaked at325nm. The emission spectra located between400and650nm and peaked at485nm, which assigned to5d-4f transition ofEu²⁺.The emission peak appeared at464nm and525nm by making theGassian fitting in the spectrum, which indicated that it exists two emissioncenters in the phosphors at least.The ions Eu²⁺occupied two different Ca²⁺ sites in the lattice sites at least. When Eu²⁺doping concentration is x=0.02inCa3-x（PO₄）₂: xEu²⁺, the phosphor had a maximum emission intensity.（3） We prepared green-emitting Ca₃（PO₄）₂:Tb³⁺phosphor under reducingatmosphere of N^2-H₂via solid-state reaction. The peak at375nm with themaximum excitation intensity corresponded to7F6â†'5L8transition of Tb³⁺inthe excitation spectra. The peak at549nm with the maximum emissionintensity was assigned to⁵D₄â†'⁷F₅transition of Tb³⁺in the emission spectra.The optimal Tb³⁺doping concentration is y=0.015in Ca_3-y³⁺（PO₄）₂:yTb³⁺phosphors.（4） We prepared blue-green emitting Ca₃（PO₄）₂:Tb³⁺,Eu²⁺phosphor underreducing atmosphere of N^2-H₂via solid-state reaction. Under378nmexcitation, there were several luminescence centers in the phosphor becauseof level broadband transition of Eu²⁺and energy level splitting of Tb³⁺. Theresults of this work will greatly provide the basis of preliminary experimentswhich can realize polychromatic and white light emitting material in thesingle matrix of Ca₃（PO₄）₂.