YAG: Ce^3 + phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some interm...YAG: Ce^3 + phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG : Ce^3 + phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG:Ce^3 +.展开更多
Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially availab...Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).展开更多
In this study,Gd^(3+)and Bi^(3+)ions act to redshift the emission band to orange region,and to enhance significantly the maximum emission of YAG:Ce^(3+).On account that size mismatch between the host and the doped Gd^...In this study,Gd^(3+)and Bi^(3+)ions act to redshift the emission band to orange region,and to enhance significantly the maximum emission of YAG:Ce^(3+).On account that size mismatch between the host and the doped Gd^(3+)ion,the crystal structure turns soft,and the emission spectra are not tuned from 540 to 570 nm but decreased the emission intensity.Accordingly,an effective way to increase emission intensity is to introduce Bi^(3+)ion into the YAG:Ce^(3+),Gd^(3+)phosphors.Experimental results show partial overlapping between the emission band of Bi^(3+)ion and the excitation band of Ce^(3+)ion,indicating that the energy transfer from Bi^(3+)to Ce^(3+)ions exists in the(Y_(1.94)Ce_(0.06)Gd)Al_(5)O_(12):Bi^(3+)phosphor.Bi^(3+)ion can serve as the activator to provide energy for Ce^(3+)ion via cross relaxation phenomenon.Therefore,the(Y_(1.94)Ce_(0.06)Gd)Al_(5)O_(12):Bi^(3+)phosphor could have potential applications in warm white LEDs.展开更多
文摘YAG: Ce^3 + phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG : Ce^3 + phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG:Ce^3 +.
基金supported by the Russian Science Foundation(No.20-73-10242)Also,this work was partially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22010301)+3 种基金the International Partnership Program of Chinese Academy of Sciences(No.121631KYSB20200039)the International Cooperation Project of Shanghai Science and Technology Commission(No.20520750200)Denis Yu.Kosyanov is grateful to the Council on grants of the President of the Russian Federation(No.SP-3221.2022.1)for supporting the studies devoted to obtaining advanced ceramic materialsThe SR XRD measurements were done at the shared research center SSTRC on the basis of the VEPP-4-VEPP-2000 complex at the Budker Institute of Nuclear Physics SB RAS.
文摘Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).
文摘In this study,Gd^(3+)and Bi^(3+)ions act to redshift the emission band to orange region,and to enhance significantly the maximum emission of YAG:Ce^(3+).On account that size mismatch between the host and the doped Gd^(3+)ion,the crystal structure turns soft,and the emission spectra are not tuned from 540 to 570 nm but decreased the emission intensity.Accordingly,an effective way to increase emission intensity is to introduce Bi^(3+)ion into the YAG:Ce^(3+),Gd^(3+)phosphors.Experimental results show partial overlapping between the emission band of Bi^(3+)ion and the excitation band of Ce^(3+)ion,indicating that the energy transfer from Bi^(3+)to Ce^(3+)ions exists in the(Y_(1.94)Ce_(0.06)Gd)Al_(5)O_(12):Bi^(3+)phosphor.Bi^(3+)ion can serve as the activator to provide energy for Ce^(3+)ion via cross relaxation phenomenon.Therefore,the(Y_(1.94)Ce_(0.06)Gd)Al_(5)O_(12):Bi^(3+)phosphor could have potential applications in warm white LEDs.