• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.6
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• pp.253-257
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• 2008

To enhance the luminescence properties, the red phosphor composed of $(Y,\;Zn)_2O_3$:$Eu^{3+}$ as doping concentration of Zn ion is synthesized at $1200^{\circ}C$ for 6 hrs in air atmosphere by conventional solid reaction method. As a result of the red phosphor $(Y,\;Zn)_2O_3$:$Eu^{3+}$ is measured X-ray diffraction (XRD), The main peak is nearly corresponded to the same as JCPDS card (No. 41-1105). When the doping concentration of Zn ion is more than 5 mol%, However, the ZnO peak is showed by XRD analysis. Therefore, when the doping concentration of Zn ion is less than 5 mol%, the Zn ion is well mixed in $Y_2O_3$ structure without the impurity phases. The photoluminescence (PL) properties is shown as this phosphor is excited in 254 nm region and the highest emission spectra of $(Y,\;Zn)_2O_3$:$Eu^{3+}$ has shown in 612 nm region because of a typical energy transition ($^5D_0{\rightarrow}^7F_2$) of $Eu^{3+}$ ion. As the doping concentration of Zn ion is more than 10 mol%, the emission peak is suddenly decreased. when the highest emission peak as doping concentration of Zn ion is shown, the composition of this phosphor is $(Y_{0.95},\;Zn_{0.05})_2O_3$:$Eu^{3+}_{0.075}$ and the particle size analyzed by FE-SEM is confirmed from 0.4 to $3{\mu}m$.

• Journal of Powder Materials
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• v.27 no.2
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• pp.146-153
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• 2020

The co-doping effect of aliovalent metal ions such as Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Zn²⁺ on the photoluminescence of the Y₂O₃:Eu³⁺ red phosphor, prepared by spray pyrolysis, is analyzed. Mg²⁺ metal doping is found to be helpful for enhancing the luminescence of Y₂O₃:Eu³⁺. When comparing the luminescence intensity at the optimum doping level of each Mg²⁺ ion, the emission enhancement shows the order of Zn²⁺ ≈ Ba²⁺ > Ca²⁺ > Sr³⁺ > Mg²⁺. The highest emission occurs when doping approximately 1.3% Zn²⁺, which is approximately 127% of the luminescence intensity of pure Y₂O₃:Eu³⁺. The highest emission was about 127% of the luminescence intensity of pure Y₂O₃:Eu³⁺ when doping about 1.3% Zn²⁺. It is determined that the reason (Y, M)₂O₃:Eu³⁺ has improved luminescence compared to that of Y₂O₃:Eu³⁺ is because the crystallinity of the matrix is improved and the non-luminous defects are reduced, even though local lattice strain is formed by the doping of aliovalent metal. Further improvement of the luminescence is achieved while reducing the particle size by using Li₂CO₃ as a flux with organic additives.

• Electrical & Electronic Materials
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• v.10 no.8
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• pp.763-769
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• 1997

In this study we have synthesized Zno:Eu phosphors under various sintering atmospheres and temperatures. The analysis of X-ray diffractometer measurement indicates that for Zno:EuCl$_3$ phosphors sintered in air and vacuum 뗘 exists in the host lattice as Eu$_2$O$_3$and EuOCl respectively. From the photoluminescence for the phosphors sintered in vacuum Eu removes the broad-band emission of the ZnO host consequently isolating the red emission due to Eu$^{3+}$ ion and improves the color purity of red emission. The photoluminescence excitation and time resolving spectrum measurements suggest that energy-transfer process occurres from the self-activated defect center in ZnO host the Eu$^{3+}$ ion which exist in the host lattice in the form of EuOCl.

• Current Optics and Photonics
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• v.2 no.1
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• pp.79-84
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• 2018

We present a novel and simple method to enable spatially selective $ZnAl_2O_4$ nanocrystal formation on the surface of $B_2O_3$-$Al_2O_3$-ZnO-CaO-$K_2O$ glass by employing localized laser heating. Optimized precipitation of glass-ceramics containing nanocrystals doped with $Eu^{3+}$ and $Yb^{3+}$ ions was performed by controlling $CO_2$ laser power and scan speed. Micro-x-ray diffraction and transmission electron microscopy revealed the mean size and morphology of nanocrystals, and energy dispersive x-ray spectroscopy showed the lateral distribution of elements in the imaged area. Laser power and scan speed controled annealing temperature for crystalization in the range of 1.4-1.8 W and 0.01-0.3 mm/s, and changed the size of nanocrystals and distribution of dopant ions. We also report more than 20 times enhanced downshift visible emission under ultraviolet excitation, and 3 times increased upconversion emission from $Eu^{3+}$ ions assisted by efficient sensitizer $Yb^{3+}$ ions in nanocrystals under 980 nm excitation. The confocal microscope revealed the depth profile of $Eu^{3+}$ ions by showing their emission intensity variation.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2523-2528
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• 2012

Green phosphors $(Zn_{1-a-b}M_aM^{\prime}_b)_xGa_yS_{x+3y/2}:Eu^{2+}$ (M, M' = alkali earth ions) with x = 2 and y = 2-5 were prepared, starting from ZnO, MgO, $SrCO_3$, $Ga_2O_3$, $Eu_2O_3$, and S with a flux $NH_4F$ using a conventional solidstate reaction. A phosphor with the composition of $(Zn_{0.6}Sr_{0.3}Mg_{0.1})_2Ga_2S_5:Eu^{2+}$ produced the strongest luminescence at a 460-nm excitation. The observed XRD patterns indicated that the optimized phosphor consisted of two components: zinc thiogallate and zinc sulfide. The characteristic green luminescence of the $ZnS:Eu^{2+}$ component on excitation at 460 nm was attributed to the donor-acceptor ($D_{ZnGa_2S_4}-A_{ZnS}$) recombination in the hybrid boundary. The optimized green phosphor converted 17.9% of the absorbed blue light into luminescence. For the fabrication of light-emitting diode (LED), the optimized phosphor was coated with MgO using magnesium nitrate to overcome their weakness against moisture. The MgO-coated green phosphor was fabricated with a blue GaN LED, and the chromaticity index of the phosphor-cast LED (pc-LED) was investigated as a function of the wt % of the optimized phosphor. White LEDs were fabricated by pasting the optimized green (G) and the red (R) phosphors, and the commercial yellow (Y) phosphor on the blue chips. The three-band pc-WLED resulted in improved color rendering index (CRI) and corrected color temperature (CCT), compared with those of the two-band pc-WLED.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.49-54
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• 2000

The new green $Al_3GdB_4O_{12}:Tb^{3+} and red Al_3GdB_4O_{12}:Eu_{3+}$ phosphors were synthesized and then characterized their optical properties for PDP application. And also the photoluminescence properties of these phosphors were compared with the commercial green $Zn_2SiO_4:Mn^{2+} and (Y,Gd)BO_3: Eu^{3+}$ red PDP phosphors. The phosphors were synthesized by solid state reaction at 115$0^{\circ}C$ for 4hr. It was found that the emitting brightness of $Al_3GdB_4O_{12}:Tb^{3+}$(15mol%) green phosphor under 147nm excitation was higher than that of commercial $Zn_2SiO_4: Mn^{2+}$ green PDP phosphor. However, the color coordinate of this new green phosphor was inferior to the commercial one. On the other hand, the emitting intensity of $Al_3GdB_4O_{12}:Eu^{3+}$(15mol%) red phosphor was smaller than the $commercial(Y,Gd)BO_3: Eu^{3+}$ red one, but the CIE coordinate was slightly improved. The excitation spectrum showed that $Al_3GdB_4O_{12}$ phosphors had a strong excitation band at $\lambda=160nm$ associated with the host absorption. And the photoluminance excitation (PLE) intensity in VUV range for $Al_3GdB_4O_{12}:Tb^{3+}$ green phosphor was higher than that of $Zn_2SiO_4: Mn^{2+}$, but the PLE intensity of $Al_3GdB_4O_{12}:Eu^{3+}$ red phosphor was smaller than $(Y,Gd)BO_3: Eu^{3+}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.4
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• pp.226-230
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• 2018

Pure $BiFeO_3$ (BFO) and codoped $Bi_{0.9}A_{0.1}Fe_{0.975}Zn_{0.025}O_{3-{\delta}}$ (A=Eu, Dy) thin films were prepared on Pt(111)/Ti/$SiO_2$/Si(100) substrates by chemical solution deposition. The remnant polarizations (2Pr) of the $Bi_{0.9}Eu_{0.1}Fe_{0.975}Zn_{0.025}O_{3-{\delta}}$ (BEFZO) and $Bi_{0.9}Dy_{0.1}Fe_{0.975}Zn_{0.025}O_{3-{\delta}}$ (BDFZO) thin films were about 36 and $26{\mu}C/cm^2$ at the maximum electric fields of 900 and 917 kV/cm, respectively, at 1 kHz. The codoped BEFZO and BDFZO thin films showed improved electrical properties, and leakage current densities of 3.68 and $1.21{\times}10^{-6}A/cm^2$, respectively, which were three orders of magnitude lower than that of the pure BFO film, at 100 kV/cm.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.2
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• pp.27-37
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• 1997

Photoluminescent and cathodoluminescent charcteristics of inorganic luminescent materials were investigated ot develop possible phosphors for thin film electroluminescent (TFEL) device applications. Mg, Zn, and Photoluminescent and cathodoluminescent charcteristics of inorganic luminescent materials were investigated ot develop possible phosphors for thin film electroluminescent (TFEL) device applications. Mg, Zn, and $Si_3N_4$ powders were used to synthesize $(Mg_xZn_{1-x})SiN_2$ host materials. $Tb_4O_7$ and $Eu_2O_3$ powdrs were added as luminescent centers. Very sharp emission spectra of $Tb^{3+}$ ions were observed from $Mg._5Zn._5SiN_2:Tb$ sampels sintered at $1400^{\circ}C$ for an hour and the maximum intensity of emission spectra occured at wavelength of 550nm (green light). Synthetic conditions of $(Mg_xZn_{1-x})SiN_2:Eu$ phosphors were optimized for the hghest luminescence. The Eu concentrations were varied from 0.2% to 1.6%. Before firing, the powders were mixed using ballmills, methanol, acetone, or D.I. water. The Mg/Zn ratio also were varied from x=0.3 to x=0.7. The maximum PL intensity was obtained from a sample with 1.2% Eu concentration and the powder was mixed with methanol and dried before firing. The maximum intensity of the emission spectra occurred t the wavelength of 470nm(blue light). TFEL devices fabricated by using sputter deposition of $(Mg._3Zn._7)SiN_2:Eu$ phosphor layer showed yellowish white emission at the phosphor field of 2MV/cm.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.790-793
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• 1996

The azacrown compound, 1,7-dioxa-4,10,13-triazacyclopentadecane-N,N',N"-tri(methyl-acetic acid)(N3O2-tri(methylacetic acid)) was synthesized by modified procedure of Krespan. Potentiometric method has been used to determine the protonation constants of N3O2-tri(methylacetic acid) and stability constants of complexes on the divalent transition metal ions (Co2+, Ni2+, Cu2+, and Zn2+) and trivalent metal ions (Ce3+, Eu3+, Gd3+, and Yb3+) with N3O2-tri(methylacetic acid). The stability constants for the complexes of the divalent transition metal ions studied in the present work with N3O2-tri(methylacetic acid) were 11.4 for Co2+, 11.63 for Ni2+, 13.51 for Cu2+, and 11.65 for Zn2+, respectively. Thus, the order of the stability constants for complexes on the transition metal ions with N3O2-tri(methylacetic acid) was shown Co2+ < Ni2+ < Cu2+ > Zn2+ as same as the order of Irving-Williams series. The stability constants of Ce3+, Eu3+, Gd3+, and Yb3+ trivalent lanthanide metal ion complexes of N3O2-tri(methylacetic acid) were, respectively, 11.26 for Ce3+, 11.56 for Eu3+, 11.49 for Gd3+, and 11.80 for Yb3+. The values of the stability constants on trivalent metal ions with the ligand are increasing according to increase atomic number, due to increase acidity. But the value of stability constant of Gd3+ ion is less than the value of Eu3+ ion. This disordered behavior is also reported by Moeller.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.735-739
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• 2002

$(Y,Gd)BO_3$: Eu, $Zn_2$$SiO_4$ : Mn and $BaMgAl_{10}$ $O_{17}$ : Eu phosphors used in PDP were continuously irradiated by vacuum ultra violet generated from the penning gas (96%Ar+4%Xe) discharge and then the change of emitting intensity with time was investigated. The brightness of these phosphors decreased exponentially with VUV excitation time. The experimental data showed that the degradation rate increased in the order of $Zn_2$$SiO_4$ : Mn>(Y,Gd)$BO_3$: Eu>$BaMgAl_{10}$ $O_{17}$ : Eu phosphor. This different degradation property of phosphors was interpreted in terms of brightness saturation and stability against VUV irradiation. It was found that the degradation property of $(Y,Gd)BO_3$ : Eu red phosphor synthesized by ultrasonic thermal spray was superior to commercial phosphor.