• Progress in Superconductivity
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• v.10 no.1
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• pp.12-16
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• 2008

In this work, nano size $BaCeO_3$, which is a possible flux pinning medium of melt processed $YBa_{2}Cu_{3}O_x$ superconductor, was synthesized by the conventional solid state reaction method using powders. $BaCeO_3$ and $CeO_2$ were mixed thoroughly using a ball milling for 24 hours and calcined at $1200^{\circ}C$ for 5 hours for the formation $BaCeO_3$ powder. The obtained $BaCeO_3$ powder was attrition milled at various milling times of 60 min, 120 min and 240 min. The $BaCeO_3$ powders of various milling times were mixed with $YBa_{2}Cu_{3}O_x$ powder. Seed melt processed $YBa_{2}Cu_{3}O_x$-$BaCeO_3$ (15wt.%) superconductors were prepared and the superconducting properties were investigated. It was found that $T_c$ of $Y_{1.5}Ba_{2}Cu_{3}O_x$ samples was not significantly affected by $BaCeO_3$ addition, but $J_c$ of samples was increased by $BaCeO_3$ addition. The $J_c$ improvement by fine $BaCeO_3$ powder (120 min attrition-milled) was effective at low magnetic fields less than 2 T.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.511-515
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• 2000

The effect of Ba2+ ion dissolution with different pH and amount of PAA on microstructural changes of green and sintered bodies and its electrical properties was studied in aqueous nano-size BaTiO3 slurry system. The dissolution of Ba2+ was least at strong base, pH 10.8 and by addition of amount of 0.15 wt% PAA. The green body with the lowest of dissolution of Ba2+ at pH 10.8 and 0.15 wt% PAA had minimum values of average pore size, 40nm and shown high increase of sintered density. The compact sintered at 125$0^{\circ}C$ for 2 hr with highest Ba2+ dissolution had low density and dielectric constant due to abnormal grian growth. However, the sintered body with the lowest Ba2+ dissolution had high sintered density and then shown high dielectric constant.

• Journal of the Korean Ceramic Society
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• v.46 no.2
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• pp.189-199
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• 2009

The Powder characteristics and sintering behavior of $SiO_2$ coated $BaTiO_3$ were studied. $BaTiO_3$ powders were synthesized by the liquid mix method developed by Pechini, and silica coating was prepared by alkoxide hydrolysis method with TEOS and ethanol. The particle size of the $BaTiO_3$ powders was 35 nm and the thickness of the $SiO_2$ coating layer was 5 nm. As the $SiO_2$ content increased, the $SiO_2$ layers improved the powder dispersion by increasing electrostatic repulsion between the $BaTiO_3$ particles. Effects of MgO coating on microstructure and dielectric properties of $BaTiO_3$ have been studied compared with mechanically MgO mixed $BaTiO_3$. MgO coated $BaTiO_3$ particles were prepared by a homogeneous precipitation method using $MgCl_2\cdot 6H_2O$ and urea. MgO coated $BaTiO_3$ exhibited homogeneous microstructure compared with mixed samples. XRD analysis revealed that Mg substitution for the Ti site in the MgO mixed sample was much greater than in the coated one. Electrical properties of MgO mixed and coated $BaTiO_3$ were affected by the diffusion behavior of Mg in $BaTiO_3$ lattice.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.8
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• pp.1068-1074
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• 1995

Effect of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ addition on the phase changes and microwave dielectric properties of BaTi $O_{3}$-3Ti $O_{2}$ ceramics were investigated. Addition of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ to BaTi $O_{3}$-3Ti $O_{2}$ resulted in the formation of Ba $Ti_{4}$$O_{9}$, $Ba_{2}$ $Ti_{9}$ $O_{20}$, Ba(Zn$_{1}$3/Nb$_{2}$3/) $O_{3}$, and Ti $O_{2}$ phases. Ba $Ti_{4}$$O_{9}$ phase was gradually transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$. This was identified by XRD and microstructure. As the Ba $Ti_{4}$$O_{9}$ phase transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$ phase, the dielectric constant increased to 37.5. Q*f$_{o}$ value was 40000 at x=0.04, and the temperature coefficient of resonant frequency was +10ppm/.deg. C.C.. C.C.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.146-150
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• 2005

Two new barium vanadium borophosphate compounds, $(NH_4)_2(C_2H_{10}N_2)_6[Ba(H_2O)_5]_2[V_2P_2BO_{12}]_6{\cdot}8H_2O$, Ba- VBPO1 and $(NH_4)_8(C_3H_{12}N_2)_4[Ba(H_2O)_7][V_2P_2BO_{12}]_6{\cdot}17H_2O$, Ba-VBPO2 have been synthesized by interdiffusion methods in the presence of diprotonated ethylenediamine and 1,3-diaminopropane. Compound Ba-VBPO1 has an infinite chain anion (${[BaH_2O)_5]_2[V_2P_2BO_{12}]_6}$$^{14-}$, whereas Ba-VBPO2 has a discrete cluster anion {[$Ba(H_2O)_7][V_2P_2BO_{12}]_6$}$^{16-}$. Crystal Data: $(NH_4)_2(C_2H_{10}N_2)_6[Ba(H_2O)_5]_2[V_2P_2BO_{12}]_6{\cdot}8H_2O$, triclinic, space group P$\overline{1}$ (no. 2), a = 13.7252(7) $\AA$, b = 15.7548(8) $\AA$, c = 15.8609(8) $\AA$, α = 63.278(1)$^{\circ}$, $\beta$ = 75.707(1)$^{\circ}$, $\gamma$ = 65.881(1)$^{\circ}$, Z = 1; $(NH_4)_8(C_3H_{12}N_2)_4[Ba(H_2O)_7][V_2P_2BO_{12}]_6{\cdot}17H_2O$, monoclinic, space group C2/c (no. 15), a = 31.347(2) $\AA$, b = 17.1221(9) $\AA$, c = 22.3058(1) $\AA$, $\beta$ = 99.303(1)$^{\circ}$, Z = 4.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.6-9
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• 1993

In this study, Sintering behavior, Crystallographic structure, Microwave Dielectric properties of the nonstoichiometric Ba$\_$1-x/(Zn$\_$1/3/Ta$\_$2/3/)O$_3$with 0 x 0.04 were investigated. A small amount(lmol%) of MnO$_2$is doped to the sample to complete the sintering. The degree of Zn and Ta ordering in B site and Lattice distortion were promoted by reducing Ba concentration. At x=0.01, Unloaded Q value reached above 7500 (at 10.5 GHZ) ; however, above x=0.01, Q value was greatly decreased, in spite of saturation in Zn-Ta ordering. At x=0.01, The Dielectric constant was 30 at 10.5GHz. and The Temperature Coefficient was estimated as 2ppm/$^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.5
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• pp.188-192
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• 2005

High $T_c(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y[(YNS)-123]$ superconductors with/without $CeO_2$ additive were systematically investigated by the zone melt growth process in air. Cylindrical green rods of (YNS)-123 oxides were fabricated by cold isostatic pressing (CIP) method using rubber mould. A sample prepared by this method showed well-textured microstructure, and $(Y_{0.5}Nd_{0.25}Sm_{0.25})_2BaCuO_5[(YNS)211]$ nonsuperconducting inclusions were uniformly dispersed in large $(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y$[(YNS)123] superconducting matrix. In this study, optimum melting temperature and growth rate were $1100^{\circ}C$ and 3 mm/hr, respectively. The directionally melt-textured (YNS)-123 sample with $CeO_2$ additive showed an onset critical temperature $(T_c)\;T_c{\geq}93K$ and sharp superconducting transition.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.6
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• pp.251-256
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• 2005

Directionally melt-textured high $T_c\;(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_{2}Cu_{3}O_y$ [(YNS)-123] superconductor was systematically investigated by the zone melt growth process in air. A sample prepared by this method showed well-textured microstructure, and $(Y_{0.5}Nd_{0.25}Sm_{0.25})_{2}BaCuO_5$[(YNS)211] inclusions were uniformly dispersed in large $(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_{2}Cu_{3}O_y$ [(YNS)123] matrix. High irreversibility field and magnetization hysteresis loop of the zone melt-textured (YNS)-123 sample exhibited the enhanced flux pinning, compared with $YBa_{2}Cu_{3}O_y$ (Y-123) sample without RE(rare earth). Critical current density of (YNS)-123 sample was $2.5{\times}10^4\;A/cm^2$ at 2 T and 77 K.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.253-258
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• 1997

The characteristics of crystal structure and phase transition with dopants ($Nb_2O_5$= 0.1~0.4 mol% and $Y_2O_3$ : 0.2~0.4 mol%) on the PTCR $BaTiO_3$ system were investigated. In the case of $Nb_2O_5$ additive, the lattice parameter of PTCR $BaTiO_3$ was changed linearly with the increasement of $Nb_2O_5$ which substituted B-site of BaTiO$_3$ and the lattice parameter of c-axis decreased abruptly at 0.3 mol%. These phenonmena were assumed to originate from the distortion of octahedron and we could confirm that the change of lattice parameter accorded with the characteristics of the phase transition temperature. $Y^{3+}$ ions substituted both of A- and B-site until the 0.3 mol% addition, but $Y^{3+}$ substitution preferred A- to B-site above 0.3 mol%. This was affirmed by the variation ,of lattice parameter and the characteristics of phase transition. It also was found that $Y^{3+}$ions in the A-site substituted both of $Ba^{2＋}$ and $Ca^{2＋}$ ions with equal ratio by Rietveld method.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.804-809
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• 2011

Tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membranes were prepared by extrusion. TGA results of green body membrane after extrusion showed three successive weight losses due to decomposition of organic additives and carbonate. Drying shrinkage rate of tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membranes was no change after 68 h and higher in the membrane with large outer diameter. XRD and SEM results showed the sintered membranes were the single phase structure and dense. The stoichiometric molar ratio agreed well with composition ratio calculated by EDS results for $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membrane. Radial crushing strength of tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membrane with 0.95 mm thickness was 5.7 kgf/$mm^2$ and the oxygen permeation rate of same membrane was 146.85 mL/min ($Jo_2$=2.33 mL/$min{\cdot}cm^2$) at $950^{\circ}C$. Therefore, it was known that use of vacuum pump was more effective than that of sweep gas to obtain higher oxygen permeation flux.