• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.679-684
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• 2000

The Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 compounds, both with Ruddlesden-Popper structures, have been synthesized by the ceramic method at $1150^{\circ}C$ under atmospheric pressure. The crystallographic structure of the compounds was assigned to the tetr agonal system with space group 14/mmm by X-ray diffraction(XRD) Rietveld refinement. The reduced lattice volume and lattice parameters increased as the Ta with 5d substitutes for the Nb with 4d in the compounds. The Co/Nb(Ta)O bond length has been determined by X-ray absorption spectroscopic(EXAFS/XANES) analysis and the XRD refinement. The CoO6,octahedra were tetragonally distorted by elongation of Co-O bond along the c-axis. The magnetic measurement shows the compounds Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 have paramagnetic properties and the Co ions with intermediate spin sates between high and low spins in D4h symmetry. All the compounds showed semiconducting behavior whose electrical conductivity increased with temperature up to 1000 K. The electrical conductiviy increased and the activation energy for the conduction decreased as the number of perovskite layers increased in the compounds with chemical formula An+1BnO3n+1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.342-342
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• 2008

The low temperature sintering and microwave dielectric properties of ceramic/glass composites which were composed of ceramics in the $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$ and zinc borosilicate glass/bismuth-zinc borosilicate glass were investigated with a view to applying the microwave dielectrics to low temperature co-fired ceramics. The $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$ addition of 5 wt% ZBS and BZBS glass ensured a successful sintering below $900^{\circ}C$. In addition, pyrochlore phase was observed in the all composition. $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$ with 5 wt% BZBS glasss demonstrated 70 as the dielectric constant ($\varepsilon_r$), 2,500 GHz as the Q$\times$f value, and -40 ppm/$^{\circ}C$ as TCF.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.333-339
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• 2003

Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BCN) has a 1:2 ordered hexagonal structure. Q-value of BCN increased with increasing sintering temperature however, it significantly decreased when the sintering temperature exceeded 140$0^{\circ}C$ Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BZN) has the 1:2 ordered hexagonal structure and the degree of the 1 : 2 ordering decreased with the increase of the sintering temperature. The Q value of the BZN increased with increasing the sintering temperature and BZN sintered at 140$0^{\circ}C$ for 6h has a maximum Q-value. For (1-x) Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$-zBa(Zn$_{1}$ 3/Nb$_{2}$ 3/)O$_3$[(1-x)BCN-xBZN] ceramics the 1:2 ordered hexagonal structure was observed in the specimens with x$\leq$0.3 and the BaNb$_{6}$ O$^{16}$ second phase was found in the specimens with x$\geq$0.6. Grain Growth, which is rotated to the BaNb$_{6}$ O$^{16}$ second phase occurred in the specimens with x$\geq$ 0.5. In this work, the excellent microwave dielectric properties of $\tau$r=0.0 ppm/$^{\circ}C$$\varepsilon$r=34.5 and Q,$\times$f=97000GHz sere obtained for the 0.7BCV-0.3BZN ceramics sintered at 1400$0^{\circ}C$ for 20h.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.925-929
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• 2009

In this study, $0.95(K_{0.5}Na_{0.5})NbO_3-0.05Li(Sb_{0.8}Nb_{0.2})O_3$ ceramics were investigated as a function of the amount of $Ag_2O$ addition in order to improve dielectric and piezoelectric properties of lead-free piezoelectric ceramics. With increasing the amount of $Ag_2O$ addition, density and electromechanical coupling factor ($k_p$) increased up to 0.2 wt.% $Ag_2O$ and decreased above 0.2 wt.% $Ag_2O$. At the sintering temperature of $1020^{\circ}C$, electromechanical coupling factor ($k_p$), density, dielectric constant (${\varepsilon}r$) and curie temperature (Tc) of ceramics with 0.2 wt% $Ag_2O$ showed the optimal values of 0.42, $4.33\;g/cm^3$, 738 and $393^{\circ}C$, respectively.

• Journal of Sensor Science and Technology
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• v.23 no.2
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• pp.105-109
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• 2014

Structure and electrical properties of $0.85NaNbO_3-0.15LiNbO_3$ ($(Li_{0.15}Na_{0.85})NbO_3$) ceramics were investigated as a function of sintering temperature. $(Li_{0.15}Na_{0.85})NbO_3$ ceramics were prepared by conventional solid state processing. A main phase of the orthorhombic perovskite structure and secondary phase of $LiNbO_3$ were confirmed for all sintered specimens. Dense $(Li_{0.15}Na_{0.85})NbO_3$ ceramics were obtained at sintering temperature above $1050^{\circ}C$. With increasing sintering temperature, the electromechanical coupling factor ($k_p$), piezoelectric constant ($d_{33}$) and relative dielectric constant (${\varepsilon}_r$) of the sintered specimens increased, while the mechanical quality factor ($Q_m$) decreased. These results are due to the increase of grain size and crystallite size of orthorhombic perovskite structure. Based on the temperature dependence of ${\varepsilon}_r$, stable piezoelectric properties were expected because no phase transition found up to $300^{\circ}C$. Typically, kp of 18%, $d_{33}$ of 34.7 pC/N, ${\varepsilon}_r$ of 135, and $Q_m$ of 62.8 were obtained for the specimens sintered at $1200^{\circ}C$ for 5 h.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.569-576
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• 1997

Electrically-induced strain and polarization studies of the (1-x)Pb(Mg1/3Nb2/3)O3-PbZrO3 crystalline solutions have been done. Dielectric constants with temperature were investigated for 0$\leq$x$\leq$0.95. With increasing PbZrO3 content the transition maxima were found to move to higher temperature region and DPT (Diffused Phase Transition) properties were decreased for x$\leq$0.60. Phase transition between ferroelectric states and antiferroelectric states was confirmed for 0.93$\times$10-3 for 0.4

• Transactions on Electrical and Electronic Materials
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• v.8 no.5
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• pp.201-205
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• 2007

Low temperature sintering behavior and microwave dielectric properties of the $BiNbO_{4^-}$ and the $ZnNb_2O_{6^-}zinc$ borosilicate glass(ZBS) systems were investigated with a view to applying the composition to LTCC technology. The addition of $10{\sim}30$ wt% ZBS in both systems ensured successful sintering below $900^{\circ}C$. For the $BiNbO_{4^-}ZBS$ system, the sintering was completed when 15 wt% ZBS was added whereas 25 wt% ZBS was necessary for the $ZnNb_2O_{6^-}zinc$ system. Secondary phase was not observed in the $BiNbO_{4^-}ZBS$ system but a small amount of $ZnNb_2O_6$ with the willemite structure as the secondary phase was observed in the $ZnNb_2O_{6^-}ZBS$ system. In terms of dielectric properties, the application of the $BiNbO_{4^-}$ and the $ZnNb_2O_{6^-}ZBS$ systems sintered at $900^{\circ}C$ to LTCC were shown to be appropriate; $BiNbO_{4^-}15$ wt% ZBS($\varepsilon_r=25,\;Q{\times}f\;value=3,700GHz,\;\tau_f=-32ppm/^{\circ}C$) and $ZnNb_2O_{6^-}25$ wt% ZBS($\varepsilon_r=15.8,\;Q{\times}f\;value=5,400GHz,\;\tau_f=-98ppm/^{\circ}C$).

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.101-103
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• 2003

The $ZnNb_2O_6$ ceramics with 5wt% CuO and $B_2O_3$(1,3,5wt%) were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $950^{\circ}C{\sim}1025^{\circ}C$ for 3hr. in air. The structural properties were investigated with sintering temperature and $B_2O_3$ addition by XRD and SEM. Also, the microwave dielectric properties were investigated with sintering temperature and $B_2O_3$ addition. Increasing the sintering temperature, the peak of second phase ($Cu_3Nb_2O_6$) was increased. But no significant difference was observed as the $B_2O_3$ addition, In the $ZnNb_2O_6$ ceramics with 5wt% CuO and 5wt% $B_2O_3$ sintered at $975^{\circ}C$ for 3hr, the dielectric constant, quality factor, temperature coefficient of the resonant frequency were 19.30, 14,662GHz, $+4.18ppm/^{\circ}C$, respectively.

• Journal of the Korean institute of surface engineering
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• v.50 no.3
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• pp.206-211
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• 2017

$BiNbO_4:RE^{3+}$ (RE = Dy, Eu, Sm, Tb) phosphors were prepared by solid-state reaction at $1100^{\circ}C$ and their structural, photoluminescent, and morphological properties were investigated. XRD patterns exhibited that all the synthesized phosphors exhibited a triclinic system with a dominant (210) diffraction peak, irrespective of the type of activator ions. The surface morphologies of rare-earth-ion-doped $BiNbO_4$ phosphors were found to depend strongly on the type of activator ions. The $Eu^{3+}$ and $Dy^{3+}$ doped $BiNbO_4$ phosphors revealed a strong red (613 nm) emission resulting from the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ and a dominant yellow (575 nm) emission originating from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of $Dy^{3+}$ respectively, which were the electric dipole transitions, indicating that the activator ions occupy sites of non-inversion symmetry in the $BiNbO_4$ phosphor. The main reddish-orange emission spectra of $Sm^{3+}$-doped $BiNbO_4$ phosphors were due to the $^4G_{5/2}{\rightarrow}^6H_{7/2}$ (607 nm) magnetic dipole transition, indicating that the $Sm^{3+}$ ions were located at inversion symmetry sites in the $BiNbO_4$ host lattice. As for $Tb^{3+}$-doped phosphors, green emission was obtained under excitation at 353 nm and its CIE chromaticity coordinates were (0.274, 0.376). These results suggest that multicolor emission can be achieved by changing the type of activator ions incorporated into the $BiNbO_4$ host crystal.

• Journal of the Korean Chemical Society
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• v.27 no.6
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• pp.424-482
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• 1983

Determination for $Ta_2O_5$,$Nb_2O_5$ and $SnO_2$ in tin slags was investigated by X-ray spectrometric method. Standard addition-dilution method was attempted and showed a comparable accuracy with standard calibration curve method. Pure chemicals($Ta_2O_5$,$Nb_2O_5$ and $SnO_2$) were added to the samples and diluted with silica or ferric oxide. For the determination of $Ta_2O_5$and$SnO_2$ , silica was more suitable than ferric oxide while the latter was more preferable than the former for $Nb_2O_5$.