• 한국표면공학회지
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• 제53권4호
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• pp.131-137
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• 2020

A series of Dy³⁺, Sm³⁺, and Dy³⁺/Sm³⁺ doped Gd₂WO₆ phosphors were synthesized by the conventional solid-state reaction. The X-ray diffraction patterns revealed that all of the diffraction peaks could be attributed to the monoclinic Gd₂WO₆ crystal structure, irrespective of the type and the concentration of activator ions. The photoluminescence (PL) excitation spectra of Dy³⁺-doped Gd₂WO₆ phosphors contained an intense charge transfer band centered at 302 nm in the range of 240-340 nm and two weak peaks at 351 and 386 nm. Under an excitation wavelength of 302 nm, the PL emission spectra consisted of two strong blue and yellow bands centered at 482 nm and 577 nm. The PL emission spectra of the Sm³⁺-doped Gd₂WO₆ phosphors had a series of three peaks centered at 568 nm, 613 nm, and 649 nm, corresponding to the ⁶G_5/2 → ⁶H_5/2, ⁶G_5/2 → ⁶H_9/2, and ⁶G_5/2 → ⁶H_11/2 transitions of Sm³⁺, respectively. The PL emission spectra of the Dy³⁺- and Sm³⁺-codoped Gd₂WO₆ phosphors showed the blue and yellow emission lines originating from the ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁴H_13/2 transitions of Dy³⁺ and reddish-orange and red emission bands due to the ⁴G_5/2 → ⁶H_7/2 and ⁴G_5/2 → ⁶H_9/2 transitions of Sm³⁺. As the concentration of Sm³⁺ increased from 1 to 15 mol%, the intensities of two PL spectra emitted by the Dy³⁺ ions gradually decreased, while those of the three emission bands due to the Sm³⁺ ions slowly increased, thus producing the color change from white to orange. The CIE color coordinates of Gd₂WO₆:5 mol% Dy³⁺, 1 mol% Sm³⁺ phosphors were (0.406, 0.407), which was located in the warm white light region.

• 한국결정성장학회지
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• 제27권1호
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• pp.42-46
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• 2017

스컬용융법으로 $SrAl_2O_4$ : $Eu^{2+}$,$Dy^{3+}$ 형광체 합성을 하였으며, 합성한 형광체의 산화물 몰비는 $SrCO_3$ : $Al(OH)_3$ : $Eu_2O_3$ : $Dy_2O_3$= 1 : 2 : 0.015 : 0.02였다. 결정구조 및 표면 형상은 X-선 회절분석과 주사전자현미경으로 규명하였다. 합성한 $SrAl_2O_4$ : $Eu^{2+}$,$Dy^{3+}$의 광학적 특성인 여기, 발광 및 장잔광 특성의 심도 있는 연구를 위해 PL(photoluminescence) 분광계로 측정하였다. PL 측정을 통해 360 nm 영역에서 여기(excitation)되고, 300~420 nm의 파장까지 여기가 일어남을 확인하였다. 발광(emission)스펙트럼은 450~600 nm의 파장에서 폭넓은 스펙트럼을 보였으며, 530 nm에서 최대 발광파장을 나타내었다. $SrAl_2O_4$ : $Eu^{2+}$,$Dy^{3+}$ 형광체는 오랜 시간 동안 발광하는 장잔광 특성을 나타내었다.

• Journal of Information Display
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• 제12권2호
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• pp.93-96
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• 2011

Single-phased $CaZrO_3:Dy^{3+}$, $Tm^{3+}$ series have been successfully synthesized by solid-state reaction, and their luminescence properties were investigated. Under 355 nm excitation, $CaZrO_3:Dy^{3+}$ series showed characteristic emission of $Dy^{3+}$, which exhibited yellowish white color. By introducing $Tm^{3+}$ into the matrix, the emitted hue of the $Dy^{3+}$-doped sample could be easily tailored to white, and simultaneously, energy transfer from $Tm^{3+}$ to $Dy^{3+}$ was observed. The color coordinates of the optimum white-emitting sample were (0.321, 0.323), which were very close to the data of the National Television Standard Committee (0.33, 0.33). The co-activated phosphors presented good match to ultraviolet light-emitting diodes (LEDs), which revealed that they could be novel promising phosphors utilized in white LED application.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1670-1672
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• 2000

The stability of ZnO-$Pr_{6}O_{11}$-CoO-$Cr_{2}O_{3}-Dy_{2}O_3$ based varistors with d.c. stress were investigated. ZnO varistor doped with 4.0 mol% $Dy_{2}O_3$ exhibited the highest nonlinear exponet, but stability was very poor because of low density. In particular, the varistor containing 0.5 mol% $Dy_{2}O_3$ showed very excellent V-I characteristic, which the nonlinear exponent was 67.39 and leakage current was 1.18 ${\mu}A$, and high stability.

• 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.

• 한국전기전자재료학회논문지
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• 제20권8호
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• pp.671-679
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• 2007

[ $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ ] phosphor was synthesized using the impregnation method, and its photoluminescence and long-afterglow properties were investigated, A mixture of $Sr(NO_3)_2,\;Al(NO_3)_2\;9H_2O,\;EuCl_3\;6H_2O,\;DyCl_3\;6H_2O,\;NdCl_3\;6H_2O$ salts were dissolved in distilled water and impregnating into the polymer precursor. After drying, the impregnated mixture was heat treated at $900-1400^{\circ}C$ for 2h in a $N_2-H_2$ reduction atmosphere. The microstructure and crystal structure of the $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ powders were examined by scanning electron microscopy and X-ray diffraction, respectively. The photoluminescence spectra showed an excitation band along over wide wavelength of 250-450nm, and a broaden emission with a maxima peak at 360nm. In addition, the spectra also showed a good long after glow that decayed over a 1000sec period after 10 min excitation illumination.

• 한국재료학회지
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• 제20권7호
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• pp.364-369
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• 2010

A $SrAl_2O_4:Eu^{2+},Dy^{3+}$ phosphor powder with stuffed tridymite structure was synthesized by glycine-nitrate combustion method. The luminescence, formation process and microstructure of the phosphor powder were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The XRD patterns show that the as-synthesized $SrAl_2O_4:Eu^{2+},Dy^{3+}$ phosphor was an amorphous phase. However, a crystalline $SrAl_2O_4 $ phase was formed by calcining at $1200^{\circ}C$ for 4h. From the SEM analysis, also, it was found that the as-synthesized $SrAl_2O_4:Eu^{2+},Dy^{3+}$ phosphor was in irregular porous particles of about 50 ${\mu}m$, while the calcined phosphor was aggregated in spherical particles with radius of about 0.5 ${\mu}m$. The emission spectrum of as-synthesized $SrAl_2O_4:Eu^{2+},Dy^{3+}$ phosphor did not appear, due to the amorphous phase. However, the emission spectrum of the calcined phosphor was observed at 520 nm (2.384eV); it showed green emission peaking, in the range of 450~650 nm. The excitation spectrum of the $SrAl_2O_4:Eu^{2+},Dy^{3+}$ phosphor exhibits a maximum peak intensity at 360 nm (3.44eV) in the range of 250~480 nm. After the removal of the pulse Xe-lamp excitation (360 nm), also, the decay time for the emission spectrum was very slow, which shows the excellent longphosphorescent property of the phosphor, although the decay time decreased exponentially.

• Archives of Metallurgy and Materials
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• 제65권4호
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• pp.1273-1276
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• 2020

Liquid metal extraction (LME) process results in 100% neodymium (Nd) extraction but the highest extraction efficiency reported for Dysprosium (Dy) so far is 74%. Oxidation of Dy is the major limiting factor for incomplete Dy extraction. In order to enhance the extraction efficiency and to further investigate the limiting factors for incomplete extraction, experiments were carried out on six different particle sizes of under 200 ㎛, 200-300 ㎛, 300-700 ㎛, 700-1000 ㎛, 1000-2000 ㎛ and over 2000 ㎛ at 900℃ with magnesium-to-magnet scrap ratio of 15:1 for 6, 24 and 48 hours, respectively. This research identified Dy₂Fe₁₇ in addition to Dy₂O₃ phase to be responsible for incomplete extraction. The relationship between Dy₂Fe₁₇ and Dy₂O₃ phase was investigated, and the overall extraction efficiency of Dy was enhanced to 97%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.330-333
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• 2002

The stability against DC accelerated aging stress of $Dy_{2}O_{3}-doped$ $ZnO-Pr_{6}O_{11}-based$ varistor ceramics was investigated. The calculated nonlinear exponent$(\alpha)$ in varistor ceramics without $Dy_{2}O_{3}$ was only 4.9, whereas the $\alpha$ value of the varistors with $Dy_{2}O_{3}$ was abruptly increased in the range of 48.8 to 58.6. The varistor ceramics with $Dy_{2}O_{3}$ content of 1.0 mol% exhibited maximum ${\alpha}$, reaching 58.6, whereas they exhibited very poor stability. While, The varistor ceramics doped with 0.5 mol% $Dy_{2}O_{3}$ exhibited not only the high nonlinearity, which the ${\alpha}$ is 55.3 and the leakage current is $0.1{\mu}A$， but also the highest stability, which the variation rates of varistor voltage and nonlinear exponent are -0.8% and -14.3%, respectively, under DC accelerated aging stress, $0.95 V_{1mA}/150^{\circ}C/24h$.

• 한국분말재료학회지
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• 제23권6호
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• pp.432-436
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• 2016

We investigate the microstructural and magnetic property changes of $DyH_2$, $Cu+DyH_2$, and $Al+DyH_2$ diffusion-treated NdFeB sintered magnets with the post annealing (PA) temperature. The coercivity of all the diffusion-treated magnets increases with increasing heat treatment temperature except at $910^{\circ}C$, where it decreases slightly. Moreover, at $880^{\circ}C$, the coercivity increases by 3.8 kOe in Cu and 4.7 kOe in Al-mixed $DyH_2$-coated magnets, whereas this increase is relatively low (3.0 kOe) in the magnet coated with only $DyH_2$. Both Cu and Al have an almost similar effect on the coercivity improvement, particularly over the heat treatment temperature range of $790-880^{\circ}C$. The diffusivity and diffusion depth of Dy increases in those magnets that are treated with Cu or Al-mixed $DyH_2$, mainly because of the comparatively easy diffusion path provided by Cu and Al owing to their solubility in the Nd-rich grain boundary phase. The formation of a highly anisotropic $(Nd,\;Dy)_2Fe_{14}B$ phase layer, which acts as the shell in the core-shell-type structure so as to prevent the reverse domain movement, is the cause of enhanced coercivity of diffusion-treated Nd-Fe-B magnets.