Ca3Sc2Si3O12:Ce3+ phosphors with single-phase were successfully synthesized by a gel-combustion method.Annealing atmosphere greatly affected the luminescent properties of the phosphor.The intensity of absorption band at 450 nm was greatly increased with a reducing atmosphere,which was very suitable as a color converter in white LED.The absorption at 243 and 311 nm was gradually enhanced with a stronger reducing atmosphere and a new absorption peak at 362 nm appeared in N2+H2 mixing gas.The emission intensity also increased when using reducing atmosphere.Meanwhile,the emission peaks slightly moved to the longer wavelength in reducing atmosphere.A white LED with higher color rending index and lower color temperature was obtained by putting our improved product Ca3Sc2Si3O12:Ce3+ green phosphor and Sr2Si5N8:Eu red phosphor onto a blue LED.
A series of Eu2+-doped CASN-sinoite multiphase system with a formula of(CaAlSiN3)(1-x)-(Si2N2O)x were successfully synthesized by the high temperature solid-state method.The crystal structure and morphology of the phosphors and their photoluminescence(PL) were investigated.For the Eu2+-doped samples the PL intensity approached its maximum when the molar ratio of Si2N2O in the samples was about 0.15.With increase of the concentration of Si2N2O,the emission peak shifted from 645 to 605 nm.It was because the spectroscopic polarizability(αsp) became smaller with the increase of Si/Al ratio or the adding of O atoms,which caused the change of crystal field strength.In addition,the full width at half maximum(FWHM) widened with the increase of x value,which was favor of the improvement of the color rendering index.
A series of Eu2+-doped ternary nitride phosphors, with a formula of(Sr1-xCax)2Si5N8:Eu2+, were synthesized by high-temperature solid-state method.The structure and luminescence properties were characterized, indicating the potential application as a red phosphor in the phosphor-converted white light-emitting diodes.The X-ray diffraction patterns showed that the Sr2Si5N8 and Ca2Si5N8 phases were generated at each end of(Sr1-xCax)2Si5N8:Eu2+ and coexisted in the range of 0.5≤x≤0.75.The emission spectra showed broad emission bands originating from the 4f65d1→4f7 transition of Eu2+ ions.The emission peak changed with the variations in Ca2+ concentration.
YAG:Ce phosphor was synthesized by a novel simple method,wherein the admixture of three raw materials(Y2O3,α-Al2O3 and CeO2) were first acidified by diluted nitric acid to prepare a precursor,followed by a high temperature heating treatment of the obtained precursor under reductive atmosphere.Through XRD measurement and SEM observation,it was found that Y2O3,one of the raw material,was firstly dissolved into the diluted nitric acid,and then recrystallized on the surface of both α-Al2O3 and CeO2 to form a novel nano-flaky hierarchical architectures with the crystalline structure of yttrium nitrate hydroxide hydrates,which makes all the precursor more homogeneous than the admixture of the raw materials from simple mechanical blending method.In the following heating process,the obtained homogeneous admixtures with hierarchical architectures could easily transform into uniform YAG:Ce phosphor.The resulted YAG:Ce phosphor exhibited higher emission intensity than the sample synthesized from mechanical mixing raw materials.
