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Al 2 O 3 –Y 3 Al 5 O 12 :Ce (Al 2 O 3 -YAG:Ce) eutectic with weak attenuation at high temperature has a wide range of applications in high-power white light solid-state lighting. However, the general color rendering index (general CRI, R a , the average value of R 1 -R 8) of phosphor-converted white light-emitting diode (Pc-WLED) based on this material is usually no higher than 70 (CCT < 6500 K). We grew Al 2 O 3 -YAG eutectics doped with three ions of Ce3+, Pr3+, and Cr3+ by the micro pulling-down (μ-PD) method to improve the R a through the co-luminescence and energy-transfer. The co-luminescence and energy-transfer were analyzed by the excitation-emission spectrum and the spectral power distribution. Results show that the energy-transfer between Ce3+ and Pr3+ ions in Al 2 O 3 -YAG:Ce, Pr occurs with each other, visibly enhancing the emission at around 610 nm and 694 nm, increases the R a by 8.4 compared to Al 2 O 3 -YAG:Ce. Moreover, the R a of the Al 2 O 3 -YAG:Ce and Al 2 O 3 -YAG:Cr stacked Pc-WLED increases by 20.4 compared to Al 2 O 3 -YAG:Ce, reaching 78.7. In addition, (R 9 , the special CRI for strong red, is 59.). In addition, the annealed (H 2) single-doped eutectics have little change compared to unannealed ones in luminescence, but the co-doped ones with multiple ions have a significant change. Significantly, the luminous efficiency of Al 2 O 3 -YAG:Ce after annealing is only increased by 4%, while that of Al 2 O 3 -YAG:Ce, Pr is increased by 13%. These studies show that the CRI of Pc-WLED base on Al 2 O 3 -YAG:Ce eutectic can be improved by ion co-doping in eutectic or superposition of Al 2 O 3 -YAG eutectic doped with other ions. • The co-luminescence of Ce3+ and Pr3+ in Al 2 O 3 –YAG enhancing the emission of 610 nm and 694 nm, increases the R a by 8.4. • The Cr3+ in Al 2 O 3 –YAG:Ce absorbs the emission spectra of the Ce3+ but quenches the fluorescence produced by Ce3+, which seriously hinders the luminescence of Ce3+. • The R a of the Al 2 O 3 –YAG:Ce and Al 2 O 3 –YAG:Cr stacked phosphor-converted LED increases by 20.4, reaching 78.7 (R 9 = 59). • The luminous efficiency of Al 2 O 3 –YAG:Ce after annealing is only increased by 4%, while that of Al 2 O 3 -YAG:Ce, Pr is increased by 13%. • It is found that the co-doping of Pr3+ ions will increase the probability of Ce4+ in Al 2 O 3 -YAG:Ce. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, single crystal of ytterbium (Yb) doped Ca5(PO4)3F (FAP) has been grown along the c-axis by using the Czochralski method. The segregation coefficients of Yb3+ in the Yb:FAP crystal has been determined by ICP-AES method. The absorption spectrum, fluorescence spectrum and fluorescence lifetime of the Yb:FAP crystal has been also measured at room temperature. In the absorption spectra, there are two absorption bands at 904 and 982nm, respectively, which are suitable for InGaAs diode laser pumping. The absorption cross-section (σ abs) is 5.117×10−20 cm2 with an FWHM of 4nm at 982nm. The emission cross-section (σ em) is 3.678×10−20 cm2 at 1042nm. Favorable values of the absorption cross-section at about 982nm are promising candidates for laser diode (LD) pumping. [Copyright &y& Elsevier]

Ce,Tb,Gd:YAG-Al 2 O 3 eutectic crystal phosphor plates (ECPPs) were grown by the micro-pulling-down (μ-PD) method to adjust correlated color temperature (CCT) and color rendering index (Ra) for high-power warm white LED applications. Tb3+ and Gd3+ ions in Ce:YAG-Al 2 O 3 play a positive role in spectra adjustment based on the structural and luminescent properties investigations. Tb3+ ions enhance the fluorescence lifetime of Ce3+ ions from 61.1 to 63.8 ns and improve the luminescence efficiency, and the highest optical-optical conversion efficiency (OCE) is 270.56 lm/W. Corresponding luminescence shift from cold white to greenish yellow. Gd3+ ions increase the peak wavelength from 554 to 564 nm and improve the Ra value, and the maximum Ra is 75.5. Corresponding luminescence is shifted from cold white to reddish violet. In addition, the luminescence of Ce,Tb,Gd:YAG-Al 2 O 3 ECPPs is adjusted to warm white with CIE coordinate (0.374, 0.364) and CCT of 4102 K, and Ra of 73.0, which is of great significance for realizing the high-power warm white LED lighting. • Tb3+ ions increased the fluorescence lifetime of Ce3+ ions by ∼17%， and improved the luminescence efficiency with the highest OCE of 270.56 lm/W. And Gd3+ ions increased the peak wavelength of emission from 554 nm to 564 nm and improved the Ra from 65.5 to 75.5. • The Ce,Tb,Gd:YAG-Al 2 O 3 ECPP has excellent performance with a low CCT of ∼4100 K and a CIE coordinate of (0.374, 0.364). • The CRI of Ce,Tb,Gd:YAG-Al 2 O 3 ECPP reached 73.0. [ABSTRACT FROM AUTHOR]

High quality Pr3+ single-doped PbF 2 and Pr3+/Yb3+ co-doped PbF 2 single crystals were grown by temperature gradient technique (TGT). By co-doping Yb3+ ion as Pr3+ ions sensitizer, the visible light emission can be regulated and the largest luminescence branching ratio can be switched from red-orange to blue-green light. Besides, when Pr3+ ions doping concentration is as low as possible, the blue light self-absorption effect can be weakened, which is beneficial to high-efficiency blue laser output. Moreover, the broad band emission around 1.3 μm from 1G 4 energy level can be observed in the Pr3+/Yb3+:PbF 2 crystal with the low maximum phonon energy for the first time. Absorption, emission spectra and luminescence mechanism are well analyzed by the energy transfer process and J-O theory. The laser upper energy level lifetime of Pr3+ ions has a great increase by Yb3+ ion effect. These advantageous spectroscopic characteristics show that the Pr3+/Yb3+:PbF 2 crystal might be potential laser gain materials for blue-green and ∼1.3 μm near-IR laser operation. • By co-doping Yb3+ ion as sensitizer for Pr3+ ions, the visible light emission can be regulated and the largest luminescence component ratio can be changed from red-orange light to blue-green light. • When doping concentration of Pr3+ ion is as low as possible, the self-absorption effect of blue light can be weakened, which is beneficial to high-efficiency blue laser output. • The broad band emission around 1.3 μm from 1G 4 energy level can be observed in the Pr3+/Yb3+: PbF 2 crystal with the low maximum phonon energy for the first time. [ABSTRACT FROM AUTHOR]

We report on the comparative growth and spectroscopy of Eu3+-doped Y 3 Al 5 O 12 (YAG) and Y 3 ScAl 4 O 12 crystals grown by the micro-pulling-down (μ-PD) method. The structure of the as-grown crystals was determined by X-ray diffraction (XRD) and Raman spectroscopy. The absorption spectra of the crystals are dominated by a strong line centered at 395 nm, matching well with the emission of commercial ultraviolet laser diodes. The Eu:YAG and Eu:Y 3 ScAl 4 O 12 crystals exhibit strongest red emission centered at 710 nm and the full width at half maximum (FWHM) was calculated to be 2.03 and 3.19 nm, respectively. The fluorescence decay curves of 5D 0 levels were measured and discussed. All the results indicate that the Eu:YAG and Eu:Y 3 ScAl 4 O 12 crystals are promising candidates for red luminescent/laser materials. • Eu:YAG and Eu:Y 3 ScAl 4 O 12 crystals were successfully grown by the micro-pulling-down technique for the first time. • The structure parameters of Eu:YAG and Eu:Y 3 ScAl 4 O 12 crystals were investigated by XRD. • Spectral parameters of Eu:YAG and Eu:Y 3 ScAl 4 O 12 crystals were obtained and compared. [ABSTRACT FROM AUTHOR]