• 한국세라믹학회지
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• 제38권8호
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• pp.705-709
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• 2001

SrTiO$_3$에 Pr$^{3+}$ 이온, 또는 Pr$^{3+}$ 이온과 Ga$^{3+}$ 이온을 첨가하여 합성한 형광체와 floating zone method로 성장시킨 단결정의 PL 특성을 조사하였다. 분말 형광체와 단결정에서 모두 Ga$^{3+}$ 이온이 함께 첨가되었을 때 적색 발광 세기가 크게 증가하였다. XRF(X-Ray Fluorescence) 측정결과 Ga$^{3+}$ 이온이 함께 첨가되었을 때 SrTiO$_3$결정 격자내의 Pr$^{3+}$ 이온의 농도가 증가하였다. Ga$^{3+}$ 이온이 함께 첨가되었을 때 적색 발광 세기가 증가하는 것은 첨가된 Ga$^{3+}$ 이온이 결정내 발광 center인 Pt$^{3+}$ 이온의 농도가 증가시켰기 때문이며, 또한 Ga$^{3+}$ 이온이 hole trap center로 작용하기 때문인 것으로 생각된다.

• 한국세라믹학회지
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• 제38권4호
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• pp.337-342
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• 2001

PDP(Plasma Display Panel)용 녹색 형광체인 Zn$_2$SiO$_4$:Mn에 채-dopant로 Al을 첨가하여 졸-겔법으로 합성하였다. 졸-겔법으로 제조한 형광체는 기존의 고상 반응에 의해 합성된 경우보다 낮은 온도(1000-110$0^{\circ}C$)에서 Zn$_2$SiO$_4$단일상을 형성하였으며, 300-500nm의 비교적 균일한 입자를 얻을 수 있었다. 또한, co-dopant인 Al을 첨가함으로써 발광휘도를 향상시키고, 전광시간을 줄일 수 있었다. 한편, TEOS의 가수분해시 $H_2O$/TEOS 비율을 조절하여 발광의 최적 조건을 조사하였다.

• 한국세라믹학회지
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• 제38권2호
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• pp.112-116
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• 2001

고상반응법에 의한 제조한 ZnGa$_2$O$_4$형광체에 Li 및 Tm 원소를 도핑함에 따른 발광특성을 조사하였다. 254nm 여기 하에서, 환원 처리된 ZnGa$_2$O$_4$형광체는 245nm에서 흡수피크와 380nm에서 발광피크를 나타내며, 이는 스피넬 구조에서 Ga$^{3+}$ 이온의 $^4$T$_2$$\longrightarrow$$^4$A$_2$천이에 기인한다. ZnGa$_2$O$_4$형광체에 있어서 Li 및 Tm을 도핑했을 경우가 도핑하지 않은 시료에 비해 발광강도 및 색순도가 개선되었으며, Li 및 Tm을 각각 0.1 mol, 0.01 mol 첨가했을 때 가장 우수한 발광강도 및 색순도 특성을 보였다.

• 한국세라믹학회지
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• 제40권7호
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• pp.652-656
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• 2003

녹색발광을 하는 스피넬 구조의 ZnGa$_2$O$_4$:Mn 형광체박막을 산소분압비를 증착변수로 이용하여 rf 마그네트론 스퍼터링법으로 증착하였으며, 증착된 박막을 산화, 진공+질소 분위기에서 각각 열처리를 하였다. 증착시 산소분압비 및 열처리시 산소분위기가 형광체 박막의 성장 및 발광특성에 미치는 영향을 관찰하였다. 열처리시 박막의 산화를 막을수록 발광특성이 향상되는 것으로 나타났다.

• 한국세라믹학회지
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• 제45권7호
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• pp.401-404
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• 2008

Willemite ($Zn_2SiO_4$) are a wide range of applications such as a phosphor host and an important crystalline phase in glass ceramics, electrical insulators, glazes, and pigments. In this study, Willemite precursors were synthesized with zinc silicate gels from mixture of zinc nitrate solution and various sodium silicate solution by the geopolymer technique. To examine the crystallization behavior, precursors were have been monitored by the XRD. A pure willemite phase was obtained at $900^{\circ}C$. TEM investigations revealed that the sample with 50 nm particle size was obtained via heat-treated at $900^{\circ}C$ for W-3.

• 한국세라믹학회지
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• 제35권8호
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• pp.801-806
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• 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.

• 한국세라믹학회지
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• 제50권1호
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• pp.50-56
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• 2013

Phosphorescent materials coated with titanium dioxide were fabricated and photocatalytic reactions between these materials and VOCs gases were examined. A thin film (approx. 100 nm) of nanosized $TiO_2$ was deposited on the $Sr_4Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^+$ phosphor using low-pressure chemical vapor deposition (LPCVD). The characteristics of the photocatalytic reaction were examined in terms of the decomposition of benzene gas using a gas chromatography (GC) system under ultraviolet (${\lambda}$ = 365 nm) and visible light (${\lambda}$ > 420 nm) irradiation. $TiO_2$-coated $Sr_4Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^+$ phosphor showed different photocatalytic behavior compared with pure $TiO_2$. $TiO_2$-coated phosphorescent materials showed a much faster photocatalytic decomposition of benzene gas under visible irradiation compared to the pure $TiO_2$ for which the result was practically negligible. This suggests that the extension of the absorption wavelength to visible light occurred through energy band bending by a heterojunction at the interface of the $Sr_4Al_{14}O_{25}-TiO_2$ composite. Also, the $Sr_4Al_{14}O_{25}-TiO_2$ composite showed the photocatalytic decomposition of benzene in darkness due to the photon light emitted from the $Sr_4Al_{14}O_{25}$ phosphors.

• 한국세라믹학회지
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• 제42권6호
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• pp.391-398
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• 2005

It is known that $BaMgAl_{10}O_{17}:Eu^{2+}(BAM)$ phosphors currently used have a serious thermal degradation problem. We screened $SrO-B_2O_3-P_2O_5$ system by a solution combinatorial chemistry technique in an attempt to search for a thermally stable blue phosphor for PDPs. A Quantitative Structure Activity Relationship (QSAR) was also obtained using an artificial neural network trained by the result fiom the combinatorial screening. As a result, we proposed a promising composition range in the $SrO-B_2O_3-P_2O_5$ ternary library. These compositions crystallized into a single major phase, $Sr_6BP_5O_{20}:Eu^{2+}$. The structure of $Sr_6BP_5O_{20}:Eu^{2+}$ was clearly determined by ab initio calculation. The luminescent efficiency of $Sr_6BP_5O_{20}:Eu^{2+}$ was 2.8 times of BAM at Vacuum Ultra Violet (VUV) excitation. The thermal stability was also good but the CIE color chromaticity was slightly poor.

• 한국세라믹학회지
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• 제45권8호
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• pp.477-481
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• 2008

$Eu^{2+}$ and $Dy^{3+}$ co-doped strontium aluminate, $SrAl_2O_4$ long phosphorescent phoshor was fabricated and its photoluminescence was characterized. The phosphor, $SrAl_2O_4:Eu^{2+},Dy^{3+}$ was synthesized by a coprecipitation in which metal salts of $Sr(NO_3)_2$, $Al(NO_3)_3{\cdot}9H_2O$, were dissolved in $(NH_4)_2CO_3$ solution with adding $Eu(NO_3)_3{\cdot}5H_2O$ and $Dy(NO_3)_3{\cdot}5H_2O$ as a activator and co-activator, respectively. The coprecipitated products were separated from solution, washed, and dried in a vacuum dry oven. The dried powders were then mixed with 3 wt% $B_2O_3$ as a flux and heated at $800{\sim}1400^{\circ}C$ for 3 h under the reducing ambient atmosphere of 95%Ar+$5%H_2$ gases. For the synthesized $SrAl_2O_4:Eu^{2+},Dy^{3+}$, properties of photoluminescence such as emission, excitation and decay time were examined. The emission intensity increased as the annealing temperature increased and showed a maximum peak intensity at 510 nm with a broad band from $400{\sim}650\;nm$. Monitored at 520 nm, the excitation spectrum showed a maximum peak intensity at $315{\sim}320\;nm$ wavelength with a broad band from $200{\sim}500\;nm$ wavelength. The decay time of $SrAl_2O_4:Eu^{2+},Dy^{3+}$ increased as the annealing temperature increased.

• 한국세라믹학회지
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• 제53권2호
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• pp.253-257
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• 2016

We added 0 ~ 5 wt% $YBO_3:Eu^{3+}$ nano powders in a scattering layer of a working electrode to improve the energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC). FESEM and XRD were used to characterize the microstructure and phase. PL and micro Raman were used to determine the fluorescence and the composition of $YBO_3:Eu^{3+}$ phosphor. A solar simulator and a potentiostat were used to confirm the photovoltaic properties of the DSSC with $YBO_3:Eu^{3+}$. From the results of the microstructure and phase of the fabricated $YBO_3:Eu^{3+}$ nano powders, we identified $YBO_3:Eu^{3+}$ having particle size less than 100 nm. Based on the microstructure and micro Raman results, we confirmed the existence of $YBO_3:Eu^{3+}$ in the scattering layer and found that it was dispersed uniformly. Through photovoltaic properties results, the maximum ECE was shown to be 5.20%, which can be compared to the value of 5.00% without $YBO_3:Eu^{3+}$. As these results are derived from conversion of light in the UV range into visible light by employing $YBO_3:Eu^{3+}$ in the scattering layer, these indicate that the ECE of a DSSC can be enhanced by employing an appropriate amount of $YBO_3:Eu^{3+}$.