• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.07a
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• pp.104-109
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• 2001

A 355 nm (3.5 eV) neodymium:yttrium aluminum gamet laser, produced by a harmonic generator, was used to create silver metallic particles as seeds for nucleation in photosensitive glass containing Ag+ and Ce3+ ions. The pulse width and frequency of the laser were 8 ns and 10 Hz, respectively. Heat treatment was conducted at 570 C for 1 h, following laser irradiation, to produce crystalline growth, after which a LiAlSi3O8 crystal phase appeared in the laser-irradiated Li2O A1203 SiO2 glass. For the Present study, we compared the effect of laser-induced crystallization on glass crystallization with that of spontaneous crystallization by heat treatment.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.787-794
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• 1995

To improvement the magnetic and frequency properties of YIG(Yttrium-Iron Garnet) in microwave region, it is investigated that the effect of $Al^{3+}$ ions on magnetic and frequency characteristics of YIG, using samples of basic YIG composition( $Y_{3}$F $e_{5}$ $O_{l2}$) added with A1$_{2}$ $O_{3}$ from 0 to 2.5 [mol%]. The measurment is conducted mainly for the structural properties and magnetical properties. The structural properties is measured using SEM(Scanning Electro Microscope), EDX(Energy-dispersive X-ray spectrometer) and XRD(X-ray diffraction equipment). The magnetical properties is measured with B-H curve tracer and impedance analyzer. As a result, it is confin-ned that the effect of eddy current loss is minimized while maintaining high saturation flux density of YIG, when YIG is added with 0.5 [mol%] of A1$_{2}$ $O_{3}$.>.>.

• Analytical Science and Technology
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• v.21 no.4
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• pp.272-278
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• 2008

Methods to separate 14 rare earth elements (REEs) and yttrium by the $AG^{(R)}$ 50W-X8 cation exchange resin, and to determine REEs by inductively coupled plasma atomic emission spectrophotometry (ICP-AES) were described. Ion exchange capacities of REEs on the resin were so high that the REEs were quantitatively ion exchanged under the flow rate of 0.3~1.0 mL/min at pH 1~6. The breakthrough capacity curve of the REEs showed that ion exchange capacities of light REEs (Cerium group) were greater than that of the heavy REEs (Yttrium group). When $200{\mu}g$ of each REEs was ion exchanged on 100 mg of resin, most of the heavy REEs were quantitatively desorbed with 10 mL of 2.0 M of $HNO_3$, while most of the light REEs with 30 mL. The method was applied to the monazite sample. The REEs could be separated from matrix, since ion exchange capacities of matrix ions of Ca, Ti, Mg, Mn were much lower than that of the REEs. However the relative standard deviations of the analytical results by the present method were not improved, as high as 1~5%.

• Journal of the Korean Chemical Society
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• v.17 no.1
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• pp.15-19
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• 1973

A method was developed for the separation of titanium, niobium and zirconium together in a group from the coexisting ions of various metals such as iron, cobalt, nickel, yttrium and rare earths by means of the cation exchange column using ${\alpha}$-hydroxyisobutyric acid as the eluent. In the course of the present investigation, it was found that the tailing phenomena of zirconium were attributable to the hydroxide precipitation which was made prior to the elution. For example, if zirconium was precipitated by sodium hydroxide, the tailing of zirconium became very serious in contrast to the results reported by others. This paper describes how these tailing phenomena of zirconium were prevented and how a practical procedure for the separation of these ions was, achieved using ion-exchange method. Using the present method the nuclides of $^{90m}Y$ and $^{90}Y$ were separated with radiochemical purity from the irradiated zirconium.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.441-442
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• 2008

For this study, Yttrium aluminum garnet (YAG) particles co-doped with $Ce^{3+}$ and $Eu^{3+}$ were prepared via the combustion process using the 1:1 ratio of metal ions to reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and photoluminescence (PL). The various YAG peaks, with the (420) main peak, appeared at all Eu concentrationin XRD patterns. The YAG phase crystallized with results that are in good agreement with the JCPDS diffraction file 33-0040. The SEM image showed that the resulting YAG:Ce,Eu powders had uniform sizes and good homogeneity. The grain size was about 50nm. The photoluminescence spectra of the YAG:Ce,Eu nanoparticles were investigated to determine the energy level of electron transition related to luminescence processes. It was composed a broad band of $Ce^{3+}$ activator into the weak line peak of $Eu^{3+}$ in YAG host. The PL intensity of $Ce^{3+}$ has the wavelengths of 480-650 nm and The PL intensity of $Eu^{3+}$ has main peak at 590nm.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.203-206
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• 2001

The effects of SrTiO$_3$ addition and sintering temperature on the microstructure and magnetic properties of yttrium iron garnet (YIG) were investigated. The lattice Parameter increasing of sintered YlG with small amount of SrTiO$_3$ addition was supposed to be substituted $Y^{+3}$, Fe$^{+3}$ ions to Sr$^{+2}$,Ti$^{+4}$ ions which are relatively large in ionic ranius. A YIG specimen sintered at 142$0^{\circ}C$ with 0.2mol% SrTiO$_3$ showed above 98% densification of theoretical density. Saturation magnetization (M$_s$) at room temperature decreased a little bit with increasing SrTiO$_3$, addition but no great chance. In addition, the coercivity (H$_c$) was almost not changed by sintering temperature.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.575-580
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• 2014

We uniformly coated Eu(III)- and Tb(III)-doped yttrium oxide onto the surface of $SiO_2$ spheres and then characterized them by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction crystallography and UV-Visible absorption. 2D and 3D photoluminescence image map profiles were reported for the core-shell type structure. Red emission peaks of Eu(III) were observed between 580 to 730 nm and assigned to $^5D_0{\rightarrow}^7F_J$ (J = 0 - 4) transitions. The green emission peaks of Tb(III) between 450 and 650 nm were attributed to the $^5D_4{\rightarrow}^7F_J$ (J = 6, 5, 4, 3) transitions. For annealed samples, Eu(III) ions were embedded at a $C_2$ symmetry site in $Y_2O_3$, which was accompanied by an increase in luminescence intensity and redness, while Tb(III) was changed to Tb(IV), which resulted in no green emission.

• Journal of the Korean Chemical Society
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• v.38 no.11
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• pp.785-791
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• 1994

The $Sr_1-_xY_xMnO_3$ (x = 0.0∼1.0) system was synthesized using amorphous citrate process. The stability of various structures and the electronic transport properties of this system were investigated. X-ray diffraction study indicated that the $Sr_1-_xY_xMnO_3$ system has three different structures depending on composition, namely, 4L-hexagonal perovskite (when x is less than 0.3), pseudocubic perovskite (when x is 0.3∼0.7), and hexagonal nonperovskite (when x is larger than 0.7) structures. The structural changes and electronic properties were interpreted based on two factors, i.e., the size of cations and the oxidation state of manganese ion. When the concentration of Y substitution exceeds 30%, the Mn-Mn repulsive interaction dominates over intermetallic attraction, and thus structure changes to pseudocubic perovskite. In perovskite phase the unit cell dimensions increases with increasing $Mn^{3+}$ ions due to yttrium substitution. The band gap of $Sr_{0.9}Y_{0.1}MnO_3$ is greater than that of $Sr_{0.5}Y_{0.5}MnO_3$. The greater band gap of $Sr_{0.9}Y_{0.1}MnO_3$ indicates that the 4L-hexagonal structure is more stabilized than cubic perovskite due to the Mn-Mn bond.

• Korean Journal of Materials Research
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• v.23 no.8
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• pp.441-446
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• 2013

There is increasing interest in zirconia as a dental material due to its aesthetics, as well as the exceptionally high fracture toughness and high strength that are on offer when it is alloyed with certain oxides like yttria. In recent years, many solution based chemical synthesis methods have been reported for synthesis of zirconia, of which the sol-gel method is considered to be best. Here, we synthesize zirconia by a sol gel assisted precipitation method using either PEG or PVA as a stabilizing agent. Zirconia sol is first synthesized using the hydrothermal method. We used NaOH as the precipitating agent in this method because it is easy to remove from the final solution. Zirconium and yttrium salts are used as precursors and PEG or PVA are used as stabilizers to separate the metal ions. The resulting amorphous zirconia powder is calcined at $900^{\circ}C$ for 2 h to get crystallized zirconia. XRD analysis confirmed the partially stabilized zirconia synthesis in all the synthesized powders. SEM was taken to check the morphology of the powder synthesized using either PEG or PVA as a stabilizing agent and finally the transparency was calculated. The results confirmed that the powder synthesized with 10 % PVA as the stabilizing agent had highest percentage of transparency among all the synthesized powder.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.506-511
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• 2008

In this study sol-gel and combustion process was surveyed for the preparation of the red $Y_2O_3$: Eu phosphor, and the properties of phosphor was considered. Chelation and hydrolysis in amorphous citrate sol-gel process were completed in initial reaction stage, and water-forming condensation was superior to organic acid-forming condensation. The mole ratio of citric acid to metal ion had to be above to for the progress of sol-gel process. The dried gel powders are mostly amorphous, and crystallize completely at $700^{\circ}C$, and the crystallinity increases with increasing calcining temperature. The luminescence property of the phosphor was analyzed by measuring the emission spectra. The luminescence intensity increases when the calcination temperature and concentration of metal ions in solution increase.