Jianjian Sun,Bijun Fang,Shuai Zhang,Zhihui Chen,Jianning Ding,Xiangyong Zhao,Haosu Luo
Er 3+ -doped Na 0.5 Bi 0.5 TiO 3 (Er-doped NBT) ceramics were prepared via a hydrothermal method . High sintering active Er-doped NBT nano cubic particles with perovskite structure were synthesized at hydrothermal condition of 200 °C for 24 h in 12 M NaOH solution, which were self-assembled via in situ crystallization mechanism by the initially as-grown nanowires. The Er-doped NBT ceramics sintered at 1100 °C for 2 h exhibit pure rhombohedral perovskite structure, high densification and rather homogenous microstructure morphology. Under 488 nm light excitation , the strong green emission peaks centering at 530 nm and 550 nm and the weak red emission peaks locating at 665 nm and 735 nm are excited, which can be attributed to the 2 H 11/2 , 4 S 3/2 , 4 F 9/2 and 4 I 9/2 → 4 I 15/2 transitions, respectively. The maximum emission intensity is obtained when the Er doping content reaches 1.0 mol%. A strong upconversion emission peak centering around 550 nm in green light range is excited under 800 nm light excitation, which is correlated with the 4 S 3/2 → 4 I 15/2 transition.
Novel efficient visible and near-infrared emitting phosphors NaY(MoO 4 ) 2 (NYM):Ln 3+ (Ln = Ce and Yb) were proposed in this work. The crystal structure, lattice vibration characteristics, morphology, and luminescent properties of NaY(MoO 4 ) 2 phosphors were described. Sensitization of Ln 3+ from the host with various doping concentrations was investigated. The yellow-green emission was achieved in Ce 3+ single-doped NYM phosphors at UV ultraviolet excitation sensitized by the MoO 4 2− group. Under UV excitation, characteristic emissions of Ce 3+ at 400–700 nm and Yb 3+ at 1000 nm of NYM:Ce,Yb were observed, enabling the spectral down-conversion applications. With the increasing concentration of Yb 3+ , the emission intensity as well as the lifetime of Ce 3+ decreased, confirming the energy transfer from Ce 3+ ions to Yb 3+ ions. And the energy transfer coefficient was 27% for NYM:0.01Ce,0.10Yb phosphor. These results indicate that the as-prepared phosphors have potential applications in optical and photonic devices.
Selectively enhanced green upconversion (UC) and near-infrared (NIR) downconversion (DC) emissions of Er 3+ by Yb 3+ -Mn 2+ dimer sensitizing have been demonstrated in Er 3+ /Yb 3+ /Mn 2+ tri-doped spinel MgGa 2 O 4 upon excitation of 980 nm laser diode (LD). By optimizing the doping rate of Mn 2+ , the intensity ratio of green to red UC emission intensities of Er 3+ (G/R) could be enhanced about 10 times. Meanwhile, the 1.5 μm NIR DC emission could also be increased about 3.6 times in this system. The DC and UC emission properties, UC mechanism, as well as the enhancing mechanism have been investigated and discussed in detail. A selectively enhancing mechanism based on Yb 3+ -Mn 2+ dimer sensitizing is proposed to explain the selectively enhancing phenomena. This work could inspire the design of novel UC materials for various applications, such as temperature sensors and optical transmission, etc.
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