• Journal of Photoscience
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• v.2 no.2
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• pp.83-87
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• 1995

Luminscence spectra and decay of crystalline hexahydro-1,3,5-trinitro-1,3,5-s-tetrazine (RDX) are observed at 90 K and the effects of photochemical reaction on the luminescence of RDX are investigated. The uv light from high power Hg lamp is used for the photochemical reaction of RDX. While no significant changes are observed in the luminescence spectra after the photochemical reaction, the intensity profile of the spectra changes with the progress of chemical reactions. The biexponential decay of luminescence is modified by chemical reactions. Features of the electronic states of crystalline RDX are discussed in relation to the luminescence.

• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.575-579
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• 1998

The 77 K luminescence and excitation spectra, and 298 K infrared and absorption spectra of $cis-{\Alpha}-[Cr(trien)Cl_2]Cl{\cdot}H_2O$ (trien=triethylenetetramine) have been measured. Ligand field electronic transitions due to spin-allowed and spin-forbidden are assigned. The zero-phonon line in the excitation spectrum splits into two components by $198\; cm^{-1}$, and the large $^2E_g$ splitting can be reproduced by the modern ligand field theory. It is confirmed that nitrogen atoms of the trien ligand have a strong σ-donor character, but chloride ligand has weak σ- and π -donor properties toward chromium(III) ion.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.854-857
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• 1996

Absorption and luminescence spectra of Eu3+ (aquo) and the two different 1: 3 Eu3+: ligand systems in aqueous solutions are measured under mild acidic pH condition. The oxydiacetate (ODA) and dipicolinate (DPA) ligands, forming the similar geometric complexes, are used in this work. The three intensity parameters, Ωλ (λ=2, 4, and 6) are empirically determined by applying the Judd-Ofelt theorem to the oscillator strengths of the six absorption bands arising from the ground 7F0 state. Among the three intensity parameters, the Ω2 is found to response markedly to a miner change in the ligand environment via the 7F0→5D0 transition. In addition, the relative oscillator strengths of the four luminescence bands in the visible region, assigned to the 5D0→7FJ (J=1, 2, 3 and 4) transitions are obtained to investigate their sensitivity to the ligand environment. Among the four bands, the 610 nm band, attributed to the 5D0→7F2 transition, shows hypersensitivity in the luminescence.

• The Korean Journal of Ceramics
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• v.2 no.3
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• pp.137-141
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• 1996

Ambient air aged anodically etched porous silicon (PS) and spark-processed silicon (sp-Si) show interesting similarities and dissimilarities in some of their luminescence-related properties. Among these similarties are: (1) the photoluminescence (PL) peak maximum in the blue/violet (410 nm);(2) the blue/violet PL peak positions are essentially unchanged with temperature ; (3) PL decay times in the nanosecond region which are independent of the detection wavelength, which is much faster in decay times compared to that of observed decay time in $SiO_2$.Among the dissimilarities are: (1) the PL intensity of blue/violet luminescence, namely, the PL intensity of sp-Si is at least 2 orders of magnitude larger than that of an ambient air aged PS; (2) the blue/violet PL intensity of sp-Si is more stable than that of ambient air aged PS under UV illuminations; (3) FTIR spectra of sp-Si favor those modes, which involve silicon -oxygen bonds in $SiO_2$ stoichiometry, whereas ambient air aged PS can be considered as a nonstoichiometric oxide judging from the observed vibrational spectra.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.181-186
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• 2007

We have investigated and analyzed the effects of the evaporation rate of MgO films on the MgO properties and the discharge characteristics of a plasma display panel(PDP). The MgO properties such as the crystal orientation, the surface roughness, the film structure, and cathode-luminescence (CL) spectra were inspected using XRD (X-ray diffraction), AFM(atomic force microscopy). And the discharging characteristics of the PDP such as the firing voltage, discharging current, and luminescence were measured using a vacuum chamber with oscilloscope (TDS 540C), current probe (TCP-312A), color meter (CS-100A) and etc. From the experiments results we confirmed the optimum evaporation rate at $5{\AA}/sec$, the MgO properties were shown to be strongly dependent on the evaporation rate, and the MgO properties had an effecton the optical and electrical characteristics. In other words, if the evaporation rates increase than $5{\AA}/sec$, the intensity of (200) orientation and cathode-luminescence (CL) spectra reduce, and the firing vlotage was increased. So the luminuous efficiency grows worse.

• Journal of the Korean institute of surface engineering
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• v.47 no.4
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• pp.192-197
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• 2014

Red-emitting nitride phosphors recently attracted considerable attention because of their high thermal stability and high color rendering index properties. For excellent phosphor of white light-emitting-diode, ternary nitride phosphor of $Sr/SmSi_5N_8:Eu^{2+}$ with different $Eu^{2+}$ ion concentration were synthesized by solid state reaction method. In this work, red-emitting nitride $Sr/SmSi_5N_8:Eu^{2+}$ phosphor was successfully synthesized by using multi-step high frequency induction heat treatment. The effects of molar ratio of component and experimental conditions on luminescence property of prepared phosphors have been investigated. The structure and luminescence properties of prepared $Sr/SmSi_5N_8:Eu^{2+}$ phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of $Sr/SmSi_5N_8:Eu^{2+}$ phosphors indicated broad excitation wavelength range of 300 - 550 nm, namely from UV to visible area with distinct enhanced emission peaks. With an increase of $Eu^{2+}$ ion concentration, the peak position of emission in spectra was red-shifted from 613 to 671 nm. After via multi-step heat treatment, prepared phosphor showed excellent luminescence properties, such as high emission intensity and low thermal quenching, better than commercial phosphor of $Y_3Al_5O_{12}:Ce^{3+}$. Using $Eu_2O_3$ as a raw material for $Eu^{2+}$ dopant with nitrogen gas flowing instead of using commercial EuN chemical for $Sr/SmSi_5N_8:Eu^{2+}$ synthesis is one of characteristic of this work.

• Journal of the Semiconductor & Display Technology
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• v.6 no.2 s.19
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• pp.65-68
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• 2007

High brightness and long persistent luminescence phosphor $CaAl_2O_4:Eu^{2+}$ was prepared with varying $Eu^{2+}$ concentration by solid state reaction technique. Synthesized materials were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}$ was observed in the blue region (${\lambda}_{max}\;=\;440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration. These materials have great potential for outdoor night time displays.

• Bulletin of the Korean Chemical Society
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• v.18 no.8
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• pp.819-823
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• 1997

The luminescence and photoexcitation spectra of cis-[Cr(cyclam)(NO3)2]NO3·½ H2O (cyclam=1,4,8,11-tetraazacyclotetradecane) taken at 77 K are reported. The infrared and visible spectra at room-temperature are also measured. The vibrational intervals of the electronic ground state are extracted from the far-infrared and emission spectra. The ten electronic bands due to spin-allowed and spin-forbidden transitions are assigned. With observed transitions, a ligand field analysis has been performed to determine the bonding property of nitrate group in the chromium(Ⅲ) complex. According to the results, it is found that nitrate ligand has weak σ- and π-donor properties toward chromium(Ⅲ).

• Journal of the Korean Ceramic Society
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• v.54 no.1
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• pp.70-74
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• 2017

Up-conversion (UC) and down-conversion (DC) luminescence of $LuNbO_4:0.18Yb^{3+}$, $xEr^{3+}$ (x = 0.01-0.07) powders were investigated. Post-annealed powders were composed of a single $LuNbO_4$ phase with a monoclinic fergusonite structure, whereas as-calcined powders contained a small amount of the $Li_3NbO_4$ impurity phase. Under near infrared radiation, the UC spectra of the post-annealed powders exhibited the strong green and weak red emission peaks assigned to the transition of $^2H_{11/2}/^4S_{3/2}$ and $^4F_{9/2}$ to the ground state ($^4I_{15/2}$) of $Er^{3+}$ ions, respectively; the green and red emission intensities were approximately 330 and 270% stronger, respectively, than those of the as-calcined powders. A two-photon UC process was involved in the emission as a result of an energy transfer from $Yb^{3+}$ to $Er^{3+}$. Under ultraviolet radiation, the DC spectra exhibited broad blue and sharp green emission bands. The DC mechanism was explained using self-activated $[NbO_4]^{3-}$ niobates and an energy transfer from $[NbO_4]^{3-}$ to $Er^{3+}$.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.35-36
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• 2000

The luminescence behaviors of Yttrium niobate and Bi doped Yttrium niobate were investigated under UV and low voltage electron excitations and interpreted with the first-principle calculations. In the UV excitation and emission spectra of $YNbO_4$ and $YNbO_4:Bi$, we were able to separate host contribution and Bi contribution and found that the shift in emission peak to longer wavelength is mainly due to Bi contribution. Using density functional theory, the cluster calculations were carried out for both $YNbO_4$ and $YNbO_4:Bi$. From the calculated density of states, we were also able to explain the charge transfer gap in the host and the effect of Bi in the excitation and emission spectra theoretically.