• 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.6 no.4
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• pp.144-148
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• 2005

The microstructure and electrical properties of varistor ceramics, which are composed of Zn-Pr­Co-Cr-Dy-oxide system, were investigated at various dysprosia $(Dy_2O_3)$ addition contents. The $DY_2O_3$ microstructurally played the role of inhibition for the densification and grain growth. As the $DY_2O_3$ content 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 nonlinear properties of varistors, above 30 in nonlinear exponent, compared with that without $DY_2O_3$. The varistors with the best performance of nonlinear properties was obtained $DY_2O_3$ content of $1.0 mol\%$, 49 in nonlinear exponent and $0.5{\mu}A$ in leakage current.

• Proceedings of the KIEE Conference
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• 2000.07c
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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.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.316-320
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• 1982

The effect of the additive on dielectric properties of $BaTiO_3$ containing 0.030 mol% $Dy_2O_3$ was investigated function of frequency from 5$\times$104 to 0.3$\times$107cps and temperature from 25 to 1$25^{\circ}C$. The dielectric constant increased with increasing $Dy_2O_3$ concentration from 0 to 0.05mol% due to space charge polarization. However, the dielectric constant decreased for further increase of $Dy_2O_3$ concentration due to density increase. The dielectric constant exhibits rapid change at the Curie temperature and the Curie temperature drops from 122 to 116$^{\circ}C$ with increasing amount of $Dy_2O_3$ concentration.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.11
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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%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.123-128
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• 2004

Both photoluminescence and the long-phosphorescent properties for $SrAl_2O_4$ : Eu$^{+2}$, $Dy^{+3}$ phosphor powder synthesized by the solid phase reaction were investigated as a function of $B_2O_3$ composition (0-10 wt%). The highest emission wavelength (520nm) of photoluminescence spectra was not affected by $B_2O_3$concentration. The highest emission intensity was obtained by the concentration of 3 wt% $B_2O_3$.After the removal of the Xenon lamp excitation (360nm), also, the excellent long-phosphorescent property of the phosphors was obtained by the concentration of 3 wt% $B_2O_3$ although the decay times for all phosphors decreased exponentially.

• Journal of Powder Materials
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• v.18 no.1
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• pp.29-34
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• 2011

In order to increase the coercivity of (Nd, Dy)-Fe-B sintered magnets without much reduction of remanence, small amount of Dy compounds such as $Dy_2O_3$ and $DyF_3$ was mixed with (Nd, Dy)-Fe-B powder. After mixing, the coercivity of (Nd, Dy)-Fe-B sintered magnets apparently increased with the increase of Dy compound in the mixture. Addition of $DyF_3$ was more effective than $Dy_2O_3$ for the improvement of coercivity. Reduction of the remanence by the addition of Dy compound, however, was larger than expected mostly due to unresolved coarse Dy compound in the magnet. EPMA analysis revealed that Dy was diffused throughout the grains in the magnet mixed with $DyF_3$ whereas Dy was rather concentrated around grain boundaries in the magnet mixed with $Dy_2O_3$.

• 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

• 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 Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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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.