• Korean Journal of Materials Research
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• v.27 no.6
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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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.5
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• pp.393-399
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• 2020

A series of phosphors, SrWO₄:5 mol% Dy³⁺, SrWO₄:5 mol% Sm³⁺, and SrWO₄:5 mol% Dy³⁺:x Sm³⁺ (x＝1~15 mol%), were prepared using a facile co-precipitation. The crystal structure, morphology, photoluminescence properties, and application in anti-counterfeiting fields were investigated. The crystalline structures of the prepared phosphors were found to be tetragonal systems with the dominant peak occurring at the (112) plane. The excitation spectra of the Dy³⁺ singly-doped SrWO₄ phosphors were composed of an intense charge-transfer band centered at 246 nm in the range of 210~270 nm and two weak peaks at 351 nm and 387 nm due to the ⁶H_15/2→⁶P_7/2 and ⁶H_15/2→⁴I_13/2 transitions of Dy³⁺ ions, respectively. The wavelength of 246 nm was optimum for exciting the luminescence of Dy³⁺ and Sm³⁺ co-doped SrWO₄ phosphors. The emission spectra consisted of two intense blue and yellow emission bands at 480 nm and 573 nm corresponding to the ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions of Dy³⁺, and two strong emission peaks at 599 nm and 643 nm originating from the ⁴G_5/2→⁶H_7/2 and ⁴G_5/2→⁶H_9/2 transitions of Sm³⁺, respectively. As the concentration of Sm³⁺ ions increased, the emission intensities of Dy³⁺ rapidly decreased, while the emission intensities of Sm³⁺ gradually increased. These results suggest that the color of the emission light can be tuned from yellow to white by changing the concentration of Sm³⁺ ions at a fixed 5 mol% Dy³⁺. Furthermore, the fluorescent security inks were synthesized for use in anti-counterfeiting applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.402-410
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• 2000

The electrical properties and stability of Pr$_{6}$/O$_{11}$-based ZnO wvaristors consisting of ZnO-Pr$_{6}$/O$_{11}$-CoO-Dy$_{2}$/O$_{3}$ based ceramics were investigated in the Dy$_{2}$/O$_{3}$ additive content range o 0.0 to 2.0 mol%. The density was nearly constant 5.62 g/cm$^3$corresponding to 97% of theoretical density as Dy$_{2}$/O$_{3}$ additive content increases up to 0.5 mol%. However the density decreased as Dy$_{2}$/O sub 3/ additive content is further additive content. Pr$_{6}$/O$_{11}$-based ZnO varistors doped with 0.5mol% Dy$_{2}$/O$_{3}$ exhibited a good nonlinearity, which is 37.76 in the nonlinear exponent and 5.36 $mutextrm{A}$ in the leakage current. And they exhibited very stress (0.80 V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85 V$_{1mA}$/115$^{\circ}C$/12h)+(0.95 V$_{1mA}$/1$25^{\circ}C$/12h). Consequently it was estimated that ZnO-0.5 mol% Pr$_{6}$/O$_{11}$-1.0 mol% CoO-0.5 mol% Dy$_{2}$/O$_{3}$ based ceramics will be sufficiently used as a basic composition to develop the advanced Pr$_{6}$/O$_{11}$-based ZnO varistors in the future.he future.uture.he future.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.234-240
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• 2007

The electrical properties and dc aging behavior for specified stress state of system, which is composed of quaternary Zn-Pr-Co-Cr, were investigated for different $Dy_2O_3$ addition doping level. As $Dy_2O_3$ doping level increased, the density decreased in the range of 5.51-4.90 $g/cm^3$, reaching maximum at 0.5 mol% and the average ZnO grain size decreased in the range of 17.7-6.0 ${\mu}m$. The incorporation of $Dy_2O_3$ significantly improved the non-ohmic properties, above 30 in non-ohmic coefficient, compared with that of undoped samples. The samples with the best performance of non-ohmic properties were obtained for $Dy_2O_3$ doping level of 1.0 mol%, with 49 in non-ohmic coefficient and 2.6 ${\mu}A/cm^2$ in leakage current. The samples with the highest stability were obtained for $Dy_2O_3$ doping level of 0.5 mol%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.5
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• pp.193-200
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• 2016

Characteristics of $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphorescent phosphors synthesized by solid state reaction and polymerized complex method were comparatively analyzed. In order to evaluate thermal stability of $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphorescent phosphors at high temperature, phosphorescent properties of $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ were investigated with thermal treatment at $1250^{\circ}C$ under reducing atmosphere, which was the general heat treatment conditions for ceramic manufacturing process. The phosphorescent properties of thermally treated $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphors synthesized by solid state reaction and polymerized complex method were investigated. The crystal structure and crystallite size were observed through XRD analysis. Microstructure and particle size of thermally treated $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphors were analyzed by SEM and PSA. Photoluminescence and afterglow characteristics of thermally treated $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphorescent phosphors were measured by spectrofluorometer.

• Advances in nano research
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• v.3 no.2
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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 $LaPO_4$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.170-170
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• 2013

형광체를 조명과 디스플레이 산업에 응용하기 위해서는 충분히 밝은 빛을 제공하는 형광체의 발광 세기가 중요한 변수이다. 이러한 발광 특성은 주로 모체 격자에 도핑 되는 활성제의 농도, 입자의 형상과 크기 분포의 균일성, 결정성에 따라 달라진다. 본 연구에서는 Ca2SiO4 모체 결정에 도핑한 활성제 Eu3+와 Dy3+ 이온의 농도를 변화시키면서 고상 반응법을 사용하여 높은 발광 효율을 갖는 Ca2-1.5xSiO4::Eux3+ 적색 형광체와 Ca2-1.5xSiO4:Dyx3+ 백색 형광체를 합성하였다. 특히, 활성제 Eu3+와 Dy3+ 이온 농도의 변화가 형광체의 결정 구조, 소성 온도, 입자의 표면 형상, 광학 스펙트럼의 발광 효율에 미치는 영향을 조사하여 최적의 합성 조건을 결정하였으며, 회절 신호의 반치폭과 발광 세기의 상호 관계를 조사하였다. Ca2-1.5xSiO4::Eux3+와 Ca2-1.5xSiO4:Dyx3+ 형광체 초기 분말 시료는 CaO (99.9% 순도), SiO2 (99.9%), Dy2O3 (99.9%)와 Eu2O3 (99.9%)인 화학 물질을 구입하여 초정밀 저울로 화학양론적으로 측정하였다. 이때 Eu와 Dy의 함량비는 x=0, 0.01, 0.05, 0.1, 0.15, 0.2 mol로 변화 시키면서 합성하였다. Ca2-1.5xSiO4: Dyx3+ 형광체 분말 시료의 경우에 소결 온도를 각각 $1000^{\circ}C$와 $1100^{\circ}C$로 달리하여 흡광과 발광 스펙트럼의 세기를 비교해 본 결과, 서로 다른 두 소결 온도에서 합성한 두 형광체 분말은 동일하게 Dy3+의 몰 비가 0.05 mol일 때 주 발광 스펙트럼의 세기는 최대값을 나타내었다. 파장 355 nm로 여기시킨 Dy3+ 함량비에 따른 Ca2-1.5xSiO4:Dyx3+ 형광체 분말의 발광 스펙트럼은 Dy3+ 함량비에 관계 없이 581 nm에서 가장 강한 황색 발광을 보였다. 함량비가 증가함에 따라 발광 스펙트럼의 변화가 관측되었는데, Dy3+의 몰 비가 0.01 mol~0.05 mol인 영역에서는 발광 세기가 증가하여 0.05 mol에서 최대를 나타내다가 Dy3+의 몰 비가 더욱 증가함에 따라 발광세기는 현저히 감소하는 경향을 나타내었는데, 이 현상은 농도 소광 현상으로 해석 할 수 있다. 이외에도, Eu3+와 Dy3+ 이온의 함량비와 소결 온도가 결정 입자의 크기와 흡광 스펙트럼에 미치는 결과를 조사하였다.

• The Korean Journal of Nuclear Medicine
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• v.28 no.2
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• pp.227-233
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• 1994

Irradiation of 20mg of natural $Dy(NO_3)_3$ in a neutron flux of $2{\times}10^{13}n/cm^2$ sec for 4 hours gave 5.76 Ci of $^{165}Dy$(specific activity, 610mCi/mg Dy) with high radionuclidic purity (>99.9 %). $^{165}Dy-MA$ was prepared in a quantitative yield by reacting the aqueous solution of $^{165}Dy(NO_3)_3$ with sodium borohydride solution in 0.2N NaOH. Coulter particle analyzer exhibited mean particle size of $2.6{\mu}m$ (range $1{\sim}6{\mu}m$), Even though the $^{165}Dy-MA$ suspension in saline was stored at $37^{\circ}C$ for 24 hours or autoclaved at $121^{\circ}C$ for 30minutes, there was no significant change in particle size and leakage problem indicating the prepared $^{165}Dy-MA$ is sufficiently stable. In-vivo retention studies were carried out by administering $^{165}Dy-MA$ into the knee joint space of normal rabbits. Gamma camera analysis showed high retention in joint space of normal rabbits. Gamma camera analysis showed high retention in joint space even at 24 hours after administration (> 99.9%). The ease with which the $^{165}Dy-MA$ can be made in the narrow size range and their high invitro and vivo stability make them attractive agents for radiation synovectomy.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1275-1276
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• 2007

For fabrication of $BaTiO_3$ system Ferroelectric thick films, (Ba,Sr,Ca)$TiO_3$ (BSCT) powders, prepared by using the alkoxide-based sol-gel method, were doped $MnCO_3$ as acceptor and $Dy_{2}O_{3}$ as donor. $MnCO_3$ and $Dy_{2}O_{3}$-doped (Ba,Sr,Ca)$TiO_3$ thick films were fabricated by screen printing techniques on high purity alumina substrates. The structure and dielectric properties were investigated with variation of $Dy_{2}O_{3}$ amount. As a result of the differential thermal analysis(DTA), exothermic peak was observed at around $670^{\circ}C$ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films, sintered at $1420^{\circ}C$ for 2h, showed the typical XRD patterns of perovskite polycrystalline structure and no pyrochlore phase was observed. The average grain size and thickness of specimens no doped with $Dy_{2}O_{3}$ was 1.32mm, 52mm, respectively. The relative dielectric constant decreased and dielectric loss increased with increasing amount of $Dy_{2}O_{3}$ dopant, the values of the BSCT thick films no doped with $Dy_{2}O_{3}$ were 4043 and 0.4% at 1 kHz, respectively. The relative dielectric constant gradually decreased in the measured frequency range from 0.1 to 100 kHz

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.134-138
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• 1997

$Dy^{3+}-(or Tm^{3+}-)$ doped $Ga_2O_3 \;and\; ZnGa_2O_4$ phosphors were prepared using the solid state reaction method to investigate their photoluminescent characteristics. Under 254 nm excitation, $Dy^{3+}-doped Ga2_O_3$ exhibited two emission bands of 460~505nm and 570~600nm. On the other hand, $Dy^{3+}-(or Tm^{3+}-)$ doped $ZnGa_2O_4 $phosphors exhibited a broad-band emission extending from 330 nm to 610 nm, peaking at about 430 nm(or 370 nm). In this study, an emission peak shift of nealy 50 nm towards longer wavelength region was observed with $Dy^{3+}$ doping in the $ZnGa_2O_4 $.