The Preparation And Luminescence Properties Of The Ce/Eu Doped Silicate/phosphate Phosphors

With the energy shortage,the development direction of research is mainly to save energy,reduce emissions,protect the environment,and seek more efficient lighting sources.Therefore,the fourth generation of lighting sources,efficient and pollution-free white LEDs,with the advantages of energy saving and environmental protection,short response time,long service life,small volume,and heat generation comparing with traditional lighting sources,using for display and lighting appears.Fluorescent conversion technology,phosphor powder coated on the LED chip,is mainly used to synthesize white LEDs.Under the excitation of short-wavelength light（such as blue and violet light）the LED chip emitted,the phosphor emits visible light.Then,the light from the LED chip and the phosphor is combined to different colors,including white light.Therefore,it is a very important topic to develop phosphors with superior performance.In this thesis,a series of single-phase phosphors doped with different doping ions are synthesized by high-temperature solid-phase method.The crystal structure,luminescence performance are characterized by XRD,fluorescence spectroscopy,fluorescence lifetime,temperature characteristics,etc.The main research results are as follows:（1）A series Na₁₅Y₃Si₁₂O₃₆:x Ce³⁺（x=0.03,0.05,0.07,0.09,0.11）;Na₁₅Y₃Si₁₂O₃₆:y Tb³⁺（y=0.03,0.05,0.07,0.09,0.11）and Na₁₅Y₃Si₁₂O₃₆:z Eu³⁺（z=0.01,0.05,0.08,0.09,0.10,0.0105,0.12,0.13）were synthesized by the high-temperature solid-phase method in the air.Na₁₅Y₃Si₁₂O₃₆:Ce³⁺phosphor emits blue light;Na₁₅Y₃Si₁₂O₃₆:Tb³⁺shows green light,and Na₁₅Y₃Si₁₂O₃₆:Eu³⁺phosphors show a pure red light.All the sample owns good color purity and good thermal stability.（2）A series of Ce³⁺/Eu²⁺single-doped and co-doped Ba₂Ca（PO₄）₂ phosphors were synthesized by the high-temperature solid-phase method under CO reducing atmosphere.It is certificated that Eu²⁺replaces the positions of Ca²⁺and Ba²⁺to form two luminescent centers through spectral testing and theoretical calculation.Energy transfer of Ce³⁺→Eu²⁺is determined in the sample by the fluorescence lifetime and emission spectrum,and the energy transfer mechanism is electric quadrupole-quadrupole interaction.The luminescent color of the Ba₂Ca（PO₄）₂:Ce³⁺phosphor is dark blue;the luminescent color of the Ba₂Ca（PO₄）₂:Eu²⁺phosphor is light blue;the luminescent color of the Ba₂Ca（PO₄）₂:0.05Ce³⁺,x Eu²⁺（x=0.005-0.04）phosphors change from dark blue as single Ce³⁺ion-doped to light blue as single Eu²⁺ion-doped.The color purity of the Ce³⁺ion emission color is 63.75%.Ba₂Ca（PO₄）₂:0.05Ce³⁺,x Eu²⁺（x=0.005-0.04）has good thermal stability from the temperature dependence luminescence.（3）A series of Ce³⁺/Eu²⁺single-doped and co-doped Ba₂Sr（PO₄）₂ phosphors were synthesized by the high-temperature solid-phase method under CO reducing atmosphere.It confirms that there is an energy transfer from Ce³⁺to Eu²⁺ions in the sample,and the energy transfer mechanism is an electric quadrupole-quadrupole interaction.The critical distance between the activator and sensitizer is 13.30（?）.The phosphor has good thermal stability from the temperature dependence emission.The color coordinates of Ba₂Sr（PO₄）₂:Ce³⁺phosphors and the color coordinates of Ba₂Sr（PO₄）₂:Eu²⁺phosphors are located in the dark blue area.The color coordinates of Ba₂Sr（PO₄）₂:0.05Ce³⁺,y Eu²⁺（y=0.005-0.03）phosphors are located in the dark blue area.（4）A series of Ce³⁺/Tb³⁺/Eu³⁺ions single and co-doped Ca₂Y₈（Si O₄）₆O₂ phosphors.Ce³⁺ions replace Y³⁺ions and Ca²⁺ion position in the Ca₂Y₈（Si O₄）₆O₂ matrix.Ce³⁺/Tb³⁺/Eu³⁺ion single-doped Ca₂Y₈（Si O₄）₆O₂ phosphor exhibit blue,cyan,and orange luminescent colors,respectively.There is an energy transfer of Ce³⁺→Tb³⁺→Eu³⁺ions in the sample from the emission spectrum and fluorescence lifetime,and the energy transfer mechanism is electric quadrupole-quadrupole interaction.The critical distance between the activator and sensitizer is 8.804（?）.The phosphor has good thermal stability from the variable temperature luminescent spectrum.The tuning of the luminous color from blue to green,and finally to white light is realized by changing the doping concentration of Tb³⁺and Eu³⁺ions in Ca₂Y₈（Si O₄）₆O₂.