Study On Synthesis And Luminescent Properities Of Phosphors With β-Ca₃（PO₄）₂ Structure

As the most outstanding member of next generation solid-state lighting sources, the white light-emitting diodes（WLEDs） have a lot of advantages compared to traditional lightings, such as energy saving, non-pollution, high safety coefficient, long life, et al. Phosphors converted white light-emitting diodes（pc-WLEDs） is the dominant way to earn white light recently, however, kinds of obvious drawbacks that existing in the system of commercial phosphors have severely limited the general application of WLEDs severely. Therefore, to explore excellent and high efficient phosphors still have a long way to go. Based on the brilliant physical and chemical properties of β-Ca₃（PO₄）₂ structure compound, a series of phosphate phosphors with this structure have been synthesized successfully by high-temperature solid-state reaction. Lastly, surround with the energy transfer theory between sensitizers and activators, the research work is carried out through different co-doped combinations of rare earth ions and transition metal ions.The red emitting phosphors Ca₉NaZn（PO₄）₇:Ce³⁺, Mn²⁺ and green emitting phosphors Ca₉NaZn（PO₄）₇:Ce³⁺, Tb³⁺ have been synthesized by high-temperature solid-state reaction. In this system, the optimum doping concentration of Ce³⁺ ions is 0.02 mol%. Under ultraviolet excitation, the emission spectra of Ca₉NaZn（PO₄）₇:Ce³⁺, Mn²⁺ consist of two broad peaks by Ce³⁺ ions（around 373 nm） and Mn²⁺ ions（around 643 nm）, similarly, the emission spectra of Ca₉NaZn（PO₄）₇:Ce³⁺, Tb³⁺ compose of two parts by Ce³⁺ broad emission peak（around 373 nm） and Tb³⁺ emission peaks（main peak at 545 nm）. The energy transfer process is running efficiently and the existence of Ce³⁺ can obviously enhance the photoluminescence performance of Mn²⁺ and Tb³⁺ ions, besides, the energy transfer mechanism of Ce³⁺ → Mn²⁺ and Ce³⁺ → Tb³⁺ have been proved to be a dipole-quadrupole interaction and a quadrupole- quadrupole interaction, and by adjusting the relative co-doping concentration of different ions, the emission colors can turn from bluish violet to red or green respectively.The new UV excitation phosphor Ca₈MgBi（PO₄）₇:Eu²⁺, Mn²⁺ has been synthesized by high-temperature solid-state reaction. The excitation spectra of this series of phosphors show a broad peak around 330 nm. Under 330 nm excitation, the Eu²⁺ ions single-doped bluish-violet emitting phosphor Ca₈MgBi（PO₄）₇:Eu²⁺ exhibits a broad emission peak around 416 nm and the Eu²⁺, Mn²⁺ ions co-doped orange-red emitting phosphor Ca₈MgBi（PO₄）₇:Eu²⁺, Mn²⁺ has two broad peaks in its emission spectrum corresponding to Ce³⁺ ions（around 373 nm） and Mn²⁺ ions（around 643 nm） respectively. The process of energy transfer from Eu²⁺ ions to Mn²⁺ ions can be observed and the mechanism has been proved to be a dipole-dipole interaction. Besides, the emission colors can be controlled by adjusting the relative doping concentration of Eu²⁺ and Mn²⁺ ions. Therefore, Ca₈MgBi（PO₄）₇:Eu²⁺, Mn²⁺ is a promising and high efficient component for UV light emitting chips white LED.A novel single-phase white-emitting phosphor Ca₁₉Mg₂（PO₄）₁₄:Ce³⁺, Tb³⁺, Mn²⁺ has been synthesized by high-temperature solid-state reaction. The photo- luminescence properties of the samples and process of energy transfer from Ce³⁺ to Tb³⁺ and Ce³⁺ to Mn²⁺ have been investigated in detail. In this system, by the action of efficient energy transfer process, the existence of Ce³⁺ ions can enhance emission intensity of Tb³⁺ and Mn²⁺ ions obviously. Under UV excitation, it was found that tri-doped phosphor Ca₁₉Mg₂（PO₄）₁₄:Ce³⁺, Tb³⁺, Mn²⁺ consists of three major parts corresponding to a broad peak of Ce³⁺ ions around 377 nm, four emission peaks of Tb³⁺ ions（ the strongest peak is located at 545 nm） and a broad emission peak of Mn²⁺ ions around 650 nm. Eventually, the white light can be obtained by regulating the relative doping concentration of Ce³⁺, Tb³⁺ and Mn²⁺ ions.