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Bharat, L. Krishna;Lee, Soo Hyun;Yu, Jae Su
- Proceedings of the Korean Vacuum Society Conference
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- 2014.02a
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- pp.415.2-415.2
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- 2014
Cost-effective, robust devices for solid-state lighting industry that converts electricity to light revolutionize the current lighting industry. Phosphor materials used in these devices should be synthesized in a low-cost and effective method for use in WLEDs. In this presentation, the synthesis of Eu3+ ions doped BaMoO4 phosphor samples by a facile synthesis process for red component of WLEDs will be shown. The tetragonal phase of the host lattice was substantiated by the X-ray diffraction patterns. The morphological studies were carried out by using a field-emission scanning electron microscope and transmission electron microscope. These confirmed the formation of a shuttle like particles with perpendicular protrusions in the middle of the particle. The photoluminescence (PL) properties exhibited good emission with a high asymmetry ratio when excited with ultraviolet B wavelengths (~ 280-315 nm). The cathodoluminescence (CL) spectra showed similar results to the PL spectra, indicating the rich red emission. The results suggest that this phosphor is a good material as red region component in the development of tri-band UV excitation based WLEDs.
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Cho, Shinho
- Current Photovoltaic Research
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- v.2 no.2
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- pp.53-58
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- 2014
$Tb^{3+}$ - or $Ce^{3+}$-doped $LaBO_3$ phosphors were synthesized by a solid-state reaction process with different concentrations of activator ions. The XRD spectra showed the monoclinic $LaBO_3$ pattern with the main peak occurring at (014) plane, irrespective of the kind of activator ions. The crystallite size was determined by using the Scherrer formula, and the maximum was obtained with an activator concentration of 0.05 mol for both phosphors. The emission spectra of $LaBO_3$ phosphors doped with $Tb^{3+}$ ions under excitation at 269 nm exhibited three major emission bands at 488, 544, and 587 nm. The strongest emission was green at 544 nm owing to the $^5D_4-^7F_5$ transition at a $Tb^{3+}$ ion concentration of 0.05 mol. For the $Ce^{3+}$-doped $LaBO_3$ phosphors, one strong blue band centered at 469 nm and weak multipeaks were observed. These results suggest that the optimum green and blue emission can be realized by controlling the concentration and type of activator ions incorporated in the host crystal.
https://doi.org/10.21218/CPR.2014.2.2.053 인용 PDF

Seong, Jiyeon;Kim, Minjin;Kim, Dong-Chan;Yoon, Il-Sang;Shin, Jaejin
- The Bulletin of The Korean Astronomical Society
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- v.46 no.2
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- pp.71.2-71.2
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- 2021
Using multi-epoch spectra of active galactic nuclei (AGN) obtained from the Sloan Digital Sky Survey, we identify 16 spectrally variable sources, for which the spectral shapes of broad emission lines significantly vary with a time scale of yrs. Out of them, 3 AGNs are already known as changing-look (CL) AGNs by previous studies. 6 AGNs are newly identified as CL AGNs from our study. A majority of these AGNs are relatively faint and their variability in the continuum is small, which may explain their non-detection in the previous studies. 7 sources are known as binary AGN candidates based on the systematic velocity offset between broad emission lines and narrow emission lines. For those sources and 3 CL AGNs, we find that the peak of broad emission lines had been shifted up to a few thousands km/s for ~10 years, implying that those can be promising candidates for pc-scale binary AGNs or recoiling black holes. We plan to conduct multiwavelength follow-up studies to nail down the physical origin of the velocity shift.
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