Study of CaTiO3:Eu3+ Red and Ca3Sc2Si3O12:Ce3+ Green Phosphors for White Light-Emitting Diode Applications

• Main Authors: Yun-FangWu, 吳昀芳
• Other Authors: In-Gann Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/21755553731717065898

博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 101 === High color purity red phosphors of Ca1-3/2xEuxTiO3 and Ca1-2xEuxLixTiO3 (0 〈 x ≤ 0.3) are synthesized via a solid-state reaction method. The red emission photoluminescence intensity and color purity are enhanced by the incorporation of Li+ into CaTiO3:Eu3+. Li+ doping increases the emission probability from 5D0 state，increase photoluminescence intensity by 1.6 times，increases color purity to 92.1%，and shortens the decay time. With increasing Eu3+ and Li+ content，the color coordinates approach the ideal red chromaticity values，coming closer than commercial Y2O2S:Eu3+ red phosphor. Ca3Sc2Si3O12:Ce3+ (CSS:Ce) green phosphors used for white light-emitting diodes (LEDs) are synthesized and co-doped with Al3+ via a solid-state reaction method. The incorporation of Al3+ into CSS:Ce can inhibit the formation of the impurity phases Sc2O3 and CeO2，improve crystallinity，and enhance the photoluminescence intensity as well as quantum efficiency. The substitution of Sc3+ with Al3+ increased the crystal field splitting of Ce3+ and resulted in the red shift of photoluminescence. The results show that Ca3Sc2-xAlxSi3O12:Ce3+ has high quantum efficiency，making it a promising green phosphor that can be collocated with a commercial 450 nm blue LED and a red phosphor for solid-state lighting applications. Al3+ co-doped Ca2.955Sc2Si3O12:Ce3+ (CSAS:Ce) green phosphors were also systematically investigated using X-ray absorption near-edge spectroscopy (XANES) to understand the influence of Al3+ incorporation on photoluminescence behavior. XANES results indicate that Al3+ occupies the Sc3+ sites and stabilizes the crystal structure of the host material. Furthermore，Al3+ can effectively inhibit the oxidization of Ce3+ to Ce4+，which enhances the photoluminescence of CSAS:Ce green phosphors. CSAS:Ce green phosphors are also synthesized by carbothermal reduction method. The structure analysis shows the doping suitable Al3+ content can inhibit residual impurity phases. Furthermore, Al3+-doping also can improve the optical properties. The optimal Al3+-doping content can upgrade from x=0.05 to x=0.15. The quantum efficiency can be enhanced from 46.8% to 51.6%. These results present that the carbothermal reduction method is better way to increase the optical performance of CSAS:Ce green phosphors, than the traditional solid-state reaction method.