• 한국표면공학회지
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• 제54권3호
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• pp.112-118
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• 2021

Dy³⁺- and Eu³⁺-codoped BaWO₄ phosphors for white light-emitting diode were synthesized with different activator ions via a solid-state reaction process. The structural, morphological, and optical properties of the BaWO₄:Dy³⁺,Eu³⁺ phosphors were investigated as a function of Eu³⁺ concentration at a fixed concentration of Dy³⁺ ions. XRD patterns exhibited that all the synthesized phosphors had a tetragonal system, irrespective of the concentrations of Dy³⁺ and Eu³⁺ ions. The excitation spectra of the synthesized phosphors were composed of three intense bands centered at 251, 355, and 393 nm and several weak peaks. For the BaWO₄:Dy³⁺,Eu³⁺ phosphors synthesized with 1 mol% of Eu³⁺, the emission spectra under ultraviolet excitation at 393 nm showed two strong blue and yellow bands at 485 and 577 nm corresponding to the ⁴F_9/2⁶H_15/2 and ⁴F_9/2⁶H_13/2 transitions of Dy³⁺ ions, respectively and several weak bands in the range of 600-700 nm resulting from the 4f transitions of Eu³⁺ ions. As the concentration of Eu³⁺ ions increased, intensities of the blue and yellow emission bands gradually decreased while those of the red emissions increased rapidly and the energy transfer efficiency from Dy³⁺ to Eu³⁺ ions was 95.3% at 20 mol% of Eu³⁺. The optimum white light emission with x=0.363, y=0.357 CIE 1931 chromaticity coordinates was obtained for the sample doped with 5 mol% Dy³⁺ and 1 mol% of Eu³⁺.

• 한국세라믹학회지
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• 제46권2호
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• pp.181-188
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• 2009

The electrical property and microstructure in $BaTiO_3$ ceramics doped rare-earth ions with intermediate ionic size ($Dy^{3+},Ho^{3+},Y^{3+}$) were investigated. Microstructures have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Incorporation of rare-earth ions to $BaTiO_3$ ceramics depended on their ionic radius sensitively. Compared to Ho and Y ions, Dy ions provide $BaTiO_3$ ceramics with the high rate of densification and well-developed shell formation, due to their high solubility in the $BaTiO_3$ lattice, but the microstructure of Dy doped $BaTiO_3$ ceramics is unstable at high temperature, because Dy ions could not play a role of grain growth inhibition, leading to diffuse into $BaTiO_3$ lattice continuously after completion of densification during sintering. Comparing electrical property and microstructure, it is shown that the reliability of capacitor improved by high shell ratio.

• 한국재료학회지
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• 제27권6호
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• pp.339-344
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• 2017

A series of $CaNb_2O_6:Dy^{3+}$, $CaNb_2O_6$:$Eu^{3+}$ and $CaNb_2O_6:Dy^{3+}$, $Eu^{3+}$ phosphors were prepared by solid-state reaction process. The effects of activator ions on the structural, morphological and optical properties of the phosphor particles were investigated. XRD patterns showed that all the phosphors had an orthorhombic system with a main (131) diffraction peak. For the $Dy^{3+}$-doped $CaNb_2O_6$ phosphor powders, the excitation spectra consisted of one broad band centered at 267 nm in the range of 210-310 nm and three weak peaks; the main emission band showed an intense yellow band at 575 nm that corresponded to the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of $Dy^{3+}$ ions. For the $Eu^{3+}$-doped $CaNb_2O_6$ phosphor, the emission spectra under ultraviolet excitation at 263 nm exhibited one strong reddish-orange band centered at 612 nm and four weak bands at 536, 593, 650, and 705 nm. For the $Dy^{3+}$ and $Eu^{3+}$-codoped $CaNb_2O_6$ phosphor powders, blue and yellow emission bands due to the $^4F_{9/2}{\rightarrow}^6H_{15/2}$ and $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transitions of $Dy^{3+}$ ions and a main reddish-orange emission line at 612 nm resulting from the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ ions were observed. As the concentration of $Eu^{3+}$ ions increased from 1 mol% to 10 mol%, the intensities of the emissions due to $Dy^{3+}$ ions rapidly decreased, while those of the emission bands originating from the $Eu^{3+}$ ions gradually increased, reached maxima at 10 mol%, and then slightly decreased at 15 mol% of $Eu^{3+}$. These results indicate that white light emission can be achieved by modulating the concentrations of the $Eu^{3+}$ ions incorporated into the $Dy^{3+}$-doped $CaNb_2O_6$ host lattice.

• 한국전기전자재료학회논문지
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• 제30권11호
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• pp.710-716
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• 2017

New white-light-emitting $SrSnO_3:Dy^{3+}$ phosphors were prepared using different concentrations of $Dy^{3+}$ ions via a solid-state reaction. The phase structure, luminescence, and morphological properties of the synthesized phosphors were investigated using X-ray diffraction analysis, fluorescence spectrophotometry, and scanning electron microscopy, respectively. All the synthesized phosphors crystallized in an orthorhombic phase with a major (020) diffraction peak, irrespective of the concentration of $Dy^{3+}$ ions. The excitation spectra were composed of a broad band centered at 298 nm, ascribed to the $O^2-Dy^{3+}$ charge transfer band and five weak bands in the range of 350~500 nm. The emission spectra of $SrSnO_3:Dy^{3+}$ phosphors consisted of three bands centered at 485, 577, and 665 nm, corresponding to the $^4F_{9/2}{\rightarrow}^6H_{15/2}$, $^4F_{9/2}{\rightarrow}^6H_{13/2}$, and $^4F_{9/2}{\rightarrow}^6H_{11/2}$ transitions of $Dy^{3+}$, respectively. As the $Dy^{3+}$ concentration increased from 1 to 15 mol%, the intensities of all the emission bands gradually increased, reached maxima at 15 mol% of $Dy^{3+}$ ions, and then decreased rapidly at 20 mol% due to concentration quenching. The critical distance between neighboring $Dy^{3+}$ ions for concentration quenching was calculated to be $9.4{\AA}$. The optimal white light emission by the $SrSnO_3:Dy^{3+}$ phosphors was obtained when the $Dy^{3+}$ concentration was 15 mol%.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.170.2-170.2
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• 2015

Enormous interest in trivalent rare-earth (RE) ions activated luminescent materials has been gaining owing to their promising applications in bio-imaging, solar cells, white light-emitting diodes and field-emission displays. Among these trivalent RE ions, dysprosium (Dy3+) was widely investigated due to its unique photoluminescence (PL) emissions. A series of Dy3+-activated CaWO4 phosphors were prepared by a facile high-temperature solid-state reaction method. The X-ray diffraction, PL spectra, cathodoluminescence (CL) spectra as well as PL decay curves were used to characterize the prepared samples. Under ultraviolet light excitation, the characteristic emissions of Dy3+ ions were observed in all the obtained phosphors. Furthermore, the PL emission intensity increased gradually with the increment of Dy3+ ion concentration, reaching its maximum value at an optimized Dy3+ ion concentration. Additionally, color-tunable emissions were obtained in Dy3+-activated CaWO4 system by adjusting the Dy3+ ion concentration and excitation wavelength. Ultimately, strong CL properties were observed in Dy3+-activted CaWO4 phosphors. These results suggested that the Dy3+-activted CaWO4 phosphors may have potential applications in the field of miniature color displays.

• 한국진공학회지
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• 제22권4호
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• pp.181-187
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• 2013

$Dy^{3+}$ 이온이 도핑된 $BaMoO_4$ 형광체 분말을 고상반응법으로 합성하였으며, 형광체의 결정 구조, 입자의 형상과 크기, 흡광과 발광 특성을 조사하였다. 모든 형광체 분말의 결정 구조는 $Dy^{3+}$ 이온의 몰 비에 관계없이 주 회절 피크 (112)를 갖는 정방 정계이었다. $Dy^{3+}$ 이온의 몰 비가 증가함에 따라 결정 입자는 용해되면서 큰 덩어리 형태의 결정 입자를 형성하였다. 흡광 스펙트럼은 293 nm에 피크를 갖는 전하 전달 밴드와 230~320 nm 영역에서 상대적으로 세기가 약한 다수의 $Dy^{3+}$ 이온의 전이 신호로 구성되었다. 발광 스펙트럼의 경우에 $Dy^{3+}$ 이온의 $^4F_{9/2}{\rightarrow}^6H_{11/2}$와 $^4F_{9/2}{\rightarrow}^6H_{9/2}$ 전이에 의한 666 nm와 754 nm에 피크를 갖는 적색 발광의 세기는 미약하였고, $^4F_{9/2}{\rightarrow}^6H_{15/2}$와 $^4F_{9/2}{\rightarrow}^6H_{13/2}$ 전이에 의한 각각 486 nm와 577 nm에 피크를 갖는 청색과 황색 발광의 세기는 상대적으로 매우 컸다. 실험 결과는 $Dy^{3+}$의 황색과 청색의 발광 세기 비를 제어함으로써 백색 발광을 구현할 수 있음을 제시한다.

• Advances in nano research
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• 제3권2호
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• pp.55-66
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• 2015

Crystalline $Ce^{3+}$ co-doped $LaPO_4$:RE ($RE=Dy^{3+}$, $Tb^{3+}$, $Eu^{3+}$, $Sm^{3+}$) and mix doped rare earth ions of $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ were prepared by the polyol method at $150^{\circ}C$. Strongly enhance luminescence intensity is obtained with the co-doping of $Ce^{3+}$ with $LaPO_4$:$Dy^{3+}$ and $LaPO_4$:$Tb^{3+}$ due to charge transfer (CT) occurring from $Ce^{3+}$ to $Dy^{3+}$ and $Ce^{3+}$ to $Tb^{3+}$, where as there is no significant changes in luminescence intensity of $Ce^{3+}$ co-doped $Eu^{3+}$ and $Sm^{3+}$ doped $LaPO_4$ samples. The luminescence color can be tuned from green to white by varying the excitation wavelength for the mix ions $Ce^{3+}$, $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ doped with $LaPO_4$.

• 한국표면공학회지
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• 제51권5호
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• pp.271-276
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• 2018

The effects of activator ion on the structural, morphological, and optical properties of $LaNbO_4:RE^{3+}$ (RE = Dy, Dy/Sm, Sm) phosphors were investigated. X-ray diffraction patterns exhibited that all the phosphors showed a monoclinic system with a main (112) diffraction peak, irrespective of the concentration and type of activator ions. The grain size showed a slightly decreasing tendency as the concentration of $Sm^{3+}$ ions increased. The excitation spectra of the $LaNbO_4:Dy^{3+}$, $Sm^{3+}$ phosphor powders consisted of a strong charge transfer band centered at 259 nm in the range of 220-290 nm and five weak peaks. The emission spectra of the $La_{0.95}NbO_4$:5 mol% $Dy^{3+}$ phosphors exhibited two intense yellow and blue bands centered at 575 nm and 479 nm respectively, which resulted from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ and $^4F_{9/2}{\rightarrow}^6H_{15/2}$ transitions of $Dy^{3+}$. As the concentration of $Sm^{3+}$ was increased, the intensity of the yellow emission band was gradually decreased, while those of orange and red emission bands centered at 604 and 646 nm began to appear and reached maxima at 5 mol%, and then decreased rapidly with further increases in the $Sm^{3+}$ concentration. These results indicated that white light emission could be realized by controlling the concentrations of the $Dy^{3+}$ and $Sm^{3+}$ ions incorporated into the $LaNbO_4$ host crystal.

• 한국진공학회지
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• 제22권2호
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• pp.79-85
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• 2013

희토류 이온 $Eu^{3+}$와 $Dy^{3+}$가 각각 도핑된 $CaMoO_4$ 광체 분말을 고상반응법으로 합성하였다. 모든 형광체 분말의 결정 구조는 활성제 이온의 종류와 농도비에 관계없이 주 회절 피크(112)를 갖는 정방 정계이었다. $Eu^{3+}$ 이온이 도핑된 형광체의 경우에, $Eu^{3+}$ 이온의 농도가 0.01~0.10 mol 영역에서 결정 입자의 크기는 전반적으로 증가하였고, 비교적 균일한 크기 분포를 가지면서 조약돌 형태를 나타내었으며, 흡광 스펙트럼은 311 nm를 정점으로 넓게 퍼져있는 전하 전달 밴드와 파장 영역 360~470nm에서 약한 피크를 갖는 다수의 흡수선이 관측되었으며, 주 발광 스펙트럼은 $Eu^{3+}$ 이온의 $^5D_0{\rightarrow}^7F_2$ 전이에 의한 618 nm에 피크를 갖는 강한 적색 발광이었다. $Dy^{3+}$ 이온이 도핑된 분말의 경우에, 흡광 스펙트럼은 303 nm에 피크를 갖는 전하 전달 밴드와 상대적으로 세기가 약한 다수의 $Dy^{3+}$ 이온의 전이 신호가 발생하였으며, 주 발광 스펙트럼은 $^4F_{9/2}{\rightarrow}^7H_{13/2}$ 전이에 의한 578 nm에 피크를 갖는 황색 발광 스펙트럼이 관측되었다.

• 한국재료학회지
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• 제26권3호
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• pp.143-148
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• 2016

$CaAl_2O_4:RE^{3+}$(RE = Tb or Dy) phosphor powders were synthesized with different contents of activator ions $Tb^{3+}$ and $Dy^{3+}$ by using the solid-state reaction method. The effects of the content of activator ions on the crystal structure, morphology, and emission and excitation properties of the resulting phosphor particles were investigated. XRD patterns showed that all the synthesized phosphors had a monoclinic system with a main (220) diffraction peak, irrespective of the content and type of $Tb^{3+}$ and $Dy^{3+}$ ions. For the $Tb^{3+}$-doped $CaAl_2O_4$ phosphor powders, the excitation spectra consisted of one broad band centered at 271 nm in the range of 220-320 nm and several weak peaks; the main emission band showed a strong green band at 552 nm that originated from the $^5D_4{\rightarrow}^7F_5$ transition of $Tb^{3+}$ ions. For the $Dy^{3+}$-doped $CaAl_2O_4$ phosphor, the emission spectra under ultraviolet excitation at 298 nm exhibited one strong yellow band centered at 581 nm and two weak bands at 488 and 672 nm. Concentration-dependent quenching was observed at 0.05 mol of $Tb^{3+}$ and $Dy^{3+}$ contents in the $CaAl_2O_4$ host lattice.