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서효진,김은식,장경혁,Liang Shi,Taiju Tsuboi,Kiyoshi Shimamura 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
The luminescence properties of Er3+ ions doped in a calcium niobium gallium garnet (Ca3(NbGa)2-xGa3O12; CNGG) crystal are investigated by using laser excitation spectroscopy. The time-resolved emission spectra of Er3+ in CNGG are measured, together with the luminescence decays caused by the 355- and 532-nm pulsed laser excitations. Different emission spectra are observed at different time delays of 250 ns and 5 μs, which suggest that presence of Er3+ ions in different environments is responsible for the observed results.
붕소함유 염수와 간수로부터 고순도 calcium borate를 합성하는 반응에 황산이 미치는 영향
서효진,김명진 한국항해항만학회 2015 한국항해항만학회지 Vol.39 No.6
본 연구에서는 붕소함유 인공염수(간수)를 수산화칼슘으로 포화시켜 calcium borate를 합성하는 반응에서, 첨가하는 황산이 미치는 영향을 알아보았다. 다양한 조건(반응온도, 반응시간, 가열반응 후 방랭온도)에서 calcium borate 합성을 시도하였고, 각 조건에서 황산 첨가유무에 따른 calcium borate의 회수율과 순도 변화를 알아보았다. XRD 분석을 통해 황산의 첨가유무에 상관없이 calcium borate(Ca2B2O5·H2O)가 생성되었음을 확인하였고, 황산을 첨가하면 부산물로 황산칼슘(CaSO4·0.5H2O)이 생성되었다. 황산을 첨가하지 않았을 때, 실험한 모든 반응온도와 반응시간 조건에서 calcium borate의 회수율과 순도가 황산을 첨가했을 때보다 더 높았다. 황산을 첨가하면 수산화칼슘의 용해도는 높아지지만, 부산물로 생성되는 황산칼슘이 calcium borate의 생성을 방해하여 그 회수율과 순도가 낮아진다고 판단된다. 본 연구에서는 붕소함유(500 mg-B/L) 인공염수(간수)에 황산을 첨가하지 않고 수산화칼슘으로 포화시켜서 80-105 ℃에서 10분 이내로 가열하여 calcium borate를 합성하였고, 그 회수율과 순도는 각각 최대 80 %, 96 %로 매우 높았다. In this study, we investigated the effects of sulfuric acid on the synthesis of calcium borate in the artificial boron-containing brine (bittern) saturated with calcium hydroxide. For the study, we attempted to synthesize calcium borate under various conditions such as reaction temperature, reaction time, and cooling temperature after heating, and then to examine the recovery and purity of the calcium borate according to the presence or absence of sulfuric acid at each condition. The XRD analysis confirmed that, regardless of the presence of sulfuric acid, the calcium borate (Ca2B2O5·H2O) was synthesized, while, in the presence of sulfuric acid, the calcium sulfate (CaSO4·0.5H2O) was produced as a by-product. In all the experiments performed by varying the reaction temperature and time, the recovery and purity of the calcium borate without sulfuric acid were observed higher than those with it. The results indicated that the addition of sulfuric acid increased the solubility of the calcium hydroxide, but the calcium sulfate produced as a by-product could decrease the recovery and purity of the calcium borate by preventing the synthesis. In this study, the artificial boron-containing brine (bittern) (500 mg-B/L) was saturated with calcium hydroxide in the absence of sulfuric acid, and then the solution was heated at 80-105 ℃ for less than 10 minutes to synthesize the calcium borate. The recovery and purity of calcium borate were measured as high as 80 % and 96 %, respectively.
Eu3+ 이온이 첨가된 란타넘텅스텐산화물의 분광학 특성
서효진,박철우 한국방사선학회 2015 한국방사선학회 논문지 Vol.9 No.1
La2W3O12:Eu3+ phosphors were prepared by solid state reaction method. The crystal structure was characterized by XRD pattern and ICSD card (78180). Luminescence properties of La2W3O12:Eu3+ are investigated by optical and laser-excitation spectroscopy in which emission and excitation spectra and time-resolved spectra are measured. The 1 mol % Eu3+-doped La2W3O12 phosphor exhibits broad excitation band peaking at 286 nm due to the ligand-to-metal charge transfer transition. The excitation lines due to the 7F0 → 5D4,5D4,5L6,5G4,5D3,5D2 transitions of Eu3+ are observed in the wavelength region 350-500 ㎚. The strong line emission is observed at 618 nm corresponding to the due to the 5D0 → 7F2 transition. The lifetime of 618 nm emission decreases with increasing temperature as 7 K (114 µs), 100 K (94 µs), 200 K (10 µs) and 300 K (0.5 µs). 본 연구는 고상법으로 형광체를 합성하였다. 모체 물질은 La2W3O12에 활성제로 Eu3+이온을 첨가하여 활성제 조성 변화에 따른 XRD 분석과 여기 및 방출 스펙트럼 및 온도에 따른 형광 스펙트럼 분석과 수명시간을 측정하였다.La2W3O12:Eu3+의 1 mol%의 XRD 스펙트럼은 ICSD 카드 (78180)에 보고된 데이터 스펙트럼과 비교하였을 때 XRD 스펙트럼이 잘 일치함을 확인 하였다. La2W3O12형광체에 활성제로 Eu3+이온 1 mol%를 첨가한 여기 스펙트럼에서는 286 nm 근처에서 286 nm 넓은 전하전달밴드가 관찰된다. 이 전하전달밴드는 WO4그룹과 Eu3+이온의 전하 전달 밴드이며 O2--W6+,O2--Eu3+의 ligand-to-metal 전하 전달 흡수가 이루어진다. 350〜500 nm 영역에서는 Eu3+의 f-f 전이에 의한 피크가 나타났다. 여기 스펙트럼에서 Eu3+의 7F0 → 5D4,5D4,5L6,5G4,5D3,5D2전이에 해당한다. 방출 스펙트럼은 280, 395 nm로 각각 여기한 결과 Eu3+이온의 5D0 → 7F2(618nm)에서 강한 피크가 보였다. 희토류 이온이 도핑 되지 않은 La2W3O12형광체를 266 nm로 여기하여 온도에 변화 따른 방출 스펙트럼은 저온에서 상온으로 갈수록 형광의 세기가 약하게 나타났다. 온도에 따른 수명시간은 7 K(114 µs), 100 K(94 µs), 200 K(10 µs), 300 K(0.5 µs)로 나타났다.
A blue-emitting phosphor of Ba2MgP4O13 : Eu2+ for white light UV light-emitting diodes
서효진,Nuan Xie,Yanlin Huang 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3
A novel blue-emitting phosphor of Eu2+-doped Ba2MgP4O13 phosphate was prepared by a high-temperature solid-state reaction method. The phosphor was investigated by X-ray powder diffraction (XRD) measurements and confirmed to be the pure crystalline phase of Ba2MgP4O13. The emission and excitation spectra of the phosphor were studied. The phosphor could be excited by UV light from 220 nm to 400 nm and emitted a blue luminescence peaked at 410 nm, which corresponds to the 4f 65d1→4f 7 transition of Eu2+ ions. The dependence of luminescence intensities of Eu2+-doped Ba2MgP4O13 on the heating temperature and doping concentrations were investigated. The phosphor had an excellent thermal stability to temperature quenching effects. The luminescence decay (lifetimes) of the phosphor is also discussed in order to further investigate its potential applications for white light-emitting diode phosphors pumped by a near-UV chip.