• Korean Journal of Materials Research
• /
• v.8 no.11
• /
• pp.999-1004
• /
• 1998

$SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 축광성 형광체의 합성에 있어서 $B_2O_3$는 일반적으로 고상반응의 촉진을 위한 플럭스로서 첨가된다. 본 연구에서는 플럭스로 첨가되는 $B_2O_3$가 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 형광체의 결정구조 및 잔광 특성에 미치는 영향을 조사하였다. 합성된 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 형광체는 520nm에서 최대 피크를 갖는 폭넓은 발광 스펙트럼을 나타내었고, $B_2O_3$ 첨가량의 5wt%일 때 최대값을 나타내었다. $B_2O_3$의 첨가에 의해 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 결정 내부에는 균일 변형(uniform strain)이 발생하였고 이 결과로 결정격자의 a축과 c축의 길이 및 $\beta$각이 감소하여다. 그리고 $SrAl_2O_4$ 결정내부의 균일 변형은 $Eu^{2+}$이온의 여기과정에서 발생하는 정공(hole)의 포획 사이트인 음이온 결함(negative defect)을 다량 발생시키는 원인이 되고, 결과적으로 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 결정의 잔광 특성을 향상시키는 것으로 생각되었다.

• Journal of Magnetics
• /
• v.15 no.4
• /
• pp.185-189
• /
• 2010

Spin polarized tunneling through a hybrid tunnel barrier of a Spin filter (SF) based on a EuO ferro-magnetic semiconductor and an organic semiconductor (OSC) (rubrene in this case) was investigated. For quasi-magnetic tunnel junction (MTJ) structures, such as Co/rubrene/EuO/Al, we observed a strong spin filtering effect of the EuO layer exhibiting I-V curves with high spin polarization (P) of up to 99% measured at 4 K. However, a magnetoresistance (MR) value of 9% was obtained at 4.2 K. The low MR compared to the high P could be attributed to spin scattering caused by structural defects at the interface between the EuO and rubrene, due to nonstoichiometry in the EuO.

• Journal of the Korean Ceramic Society
• /
• v.35 no.8
• /
• pp.801-806
• /
• 1998

$Eu^{3+}$ -doped $Y_2$$O_3$ phosphors has been prepared by a polymerized complex method and investigated their powder and luminescence properties. They were compared with phosphors prepared by a solid state reac-thion method. The phosphors synthesized have been characterized by X-ray diffraction low-voltage lu-minescent emission spectroscopy etc. Under low-voltage electron excitation $Eu^{3+}$-doped $Y_2$$O_3$ exhibited a strong narrow-band red emission peaking at 612nm. On the other hand the critical value for concentration quenching of sample prepared by the polymerized complex method fired at $1400^{\circ}C$ is x=0.05 for $(Y_{1-x}Eu_x__2O_3$ The emission intensity of phosphors prepared by the polymerized complex method was higher than that of phosphors prepared by the solid state reaction method.

• Journal of the Korean institute of surface engineering
• /
• v.54 no.2
• /
• pp.96-101
• /
• 2021

NaNbO₃:Eu³⁺ phosphor thin films were grown on quartz substrates by radio-frequency magnetron sputtering at a growth temperature of 100 ℃, with subsequent annealing at temperatures of 800, 900, and 1000 ℃. The effects of annealing temperature on the structural, morphological, and optical properties of the thin films were investigated. The NaNbO₃:Eu³⁺ sputtering target was synthesized by a solid-state reaction of raw materials Na₂CO₃, Nb₂O₅, and Eu₂O₃. The X-ray diffraction patterns exhibited that the thin films had two mixed phases of NaNbO₃ and Eu₂O₃. Surface morphologies were investigated by using field emission-scanning electron microscopy and indicated that the grains of the thin film annealed at 1000 ℃ showed irregular shapes with an average size of approximately 300 nm. The excitation spectra of Eu³⁺-doped NaNbO₃ thin film consisted of a strong charge transfer band centered at 304 nm in the range of 240-350 nm and two weak peaks at 395 and 462 nm, respectively, resulting from the ⁷F₀→⁵L₆ and ⁷F₀→⁵H₂ transitions of Eu³⁺ ions. The emission spectra under excitation at 304 nm exhibited an intense red band centered at 614 nm and two weak bands at 592 and 681 nm. As the annealing temperature increased from 800 ℃ to 1000 ℃, the intensities of all the emission bands and the band gap energies gradually increased. These results indicate that the higher annealing temperature enhance the luminescent properties of NaNbO₃:Eu³⁺ thin films.

• Applied Chemistry for Engineering
• /
• v.32 no.4
• /
• pp.478-482
• /
• 2021

The catalytic yields of partial oxidation of methane (POM) to hydrogen over Ln(1)-Ni(5)/SBA-15 (Ln = Dy, Eu, Pr, and Tb) were investigated in a fixed bed flow reactor under atmosphere. As 1 wt% of Eu was added to Ni(5)/SBA-15 catalyst, the O1s and Si2p core electron levels of Eu(1)-Ni(5)/SBA-15 showed the chemical shift by XPS. XPS analysis also demonstrated that the atomic ratio of O1s, Ni2p_3/2, and Si2p increased to 1.284, 1.298, and 1.058, respectively, and exhibited O^-, and O^2- oxygen and metal ions such as Eu³⁺, Ni⁰, Ni²⁺, and Si⁴⁺ on the catalyst surface. The yield of hydrogen on the Eu(1)-Ni(5)/SBA-15 was 57.2%, which was better than that of Ln(1)-Ni(5)/SBA-15 (Ln = Dy, Pr, and Tb), the catalytic activity was kept steady even 25 h. As 1 wt% of Eu was added to Ni(5)/SBA-15, the oxygen vacancies caused by strong metal-support interaction (SMSI) effect due to the strong interaction between metals and carrier are made. They are resulted in increasing the dispersion of Ni⁰, and Ni²⁺ nano particles on the surface of catalyst, and are kept catalytic activity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.3
• /
• pp.258-263
• /
• 2002

We present a new toed phosphor, $Gd_{2-x-y}Li_xEu_yO_3$ with superior luminescent Properties compared to the commercially available red phosphor $Y_2O_3:Eu^{3+}$. The phosphor, with a diameter of about $2\mu\textrm{m}$, consists of the psedospherical particles in a regular array. The photoluminescence measurements as a function of the laser power and the Eu mole fraction were performed at zoom temperature The luminescence intensity linearly increases as both the laser power and the Eu mole fraction Increase. As for the dependence on cathodoluminescence, the incorporation of Eu and Li ions into $Gd_2O_3$ lattice brings about an increase in luminescent efficiency. The highest emission intensity for the phosphor occurs at the applied voltage of 500 V, its value is larger than that of $Y_2O_3:Eu^{3+}$ powder by 70%.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.14 no.3
• /
• pp.123-128
• /
• 2004

Both photoluminescence and the long-phosphorescent properties for $SrAl_2O_4$ : Eu$^{+2}$, $Dy^{+3}$ phosphor powder synthesized by the solid phase reaction were investigated as a function of $B_2O_3$ composition (0-10 wt%). The highest emission wavelength (520nm) of photoluminescence spectra was not affected by $B_2O_3$concentration. The highest emission intensity was obtained by the concentration of 3 wt% $B_2O_3$.After the removal of the Xenon lamp excitation (360nm), also, the excellent long-phosphorescent property of the phosphors was obtained by the concentration of 3 wt% $B_2O_3$ although the decay times for all phosphors decreased exponentially.

• Transactions on Electrical and Electronic Materials
• /
• v.15 no.5
• /
• pp.249-252
• /
• 2014

The aim of this work is to investigate the effect of $Ca_xSr_{2-x}$ and activator on the structural and luminescent properties of green-emitting $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ nano phosphor. Using urea as fuel and ammonium nitrate as oxidizer, $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ has been successfully synthesized, using a combustion method. The particles were found to be small, spherical and of round surface. SEM imagery showed that the phosphors particles are of nanosize. The $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ emission spectrum for 360 nm excitation showed a single band, with a peak at 490 nm, which is a green emission. The highest luminous intensity was at $1,000^{\circ}C$, which was obtained when the $Eu^{2+}$ content (y) was 0.05. The results support the application of $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor as a fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). Characteristics of the synthesized $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and photoluminescence (PL) detection.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.811-814
• /
• 2002

$(Ba,Sr)_2SiO_4:Eu^{2+}$ phosphor particles with high brightness were prepared by spray pyrolysis. The changes in the photoluminescence intensity and morphology of $(Ba,Sr)_2SiO_4:Eu^{2+}$ were investigated by changing the posttreatment temperature and the concentration of dopant. The prepared $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles has a dense structure, but irregular shape after the posttreatment. When they were excited by the ultraviolet light of 410 nm, a broad emission band with a peak at 508 nm was observed. The photoluminescence intensity of the prepared $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles was enhanced by increasing the posttreatment temperature up to 1300 $^{\circ}C$ and further improved by adding several rear-earth codopants. The $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles prepared by spray pyrolysis had a good excitation spectrum in the wavelength longer than 350 nm. Therefore, it was concluded that the $(Ba,Sr)_2SiO_4:Eu^{2+}$ prepared by spray pyrolysis is a good green-emitting phosphor for LED application.

• Journal of the Korean Chemical Society
• /
• v.45 no.3
• /
• pp.236-241
• /
• 2001

Europium activated yttrium oxide ($Y_2O_3$ : Eu) is extensively applied to red phosphor for Flat Panel Display because of its high efficiency and the thermal and chemical stability. Flat Panel Display screen which have a high resolution and high efficiency needs to the phosphors of ideally small size spherical particle. In this study, we prepared a $Y_2O_3$ : Eu phosphor using polymeric precursor methods and investigated the codoping effect by introducing the group 1 or 2 elements to $Y_2O_3$ : Eu phosphor in view of improvement of luminance efficiency.