• Electrical & Electronic Materials
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• v.9 no.4
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• pp.379-384
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• 1996

The microwave dielectric properties of (I-x)CaTiO$_{3}$-xLaAIO$_{3}$ were investigated. The solid solution of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ had the perovskite structure in the range of all compositions. The crystal system of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ was transformed to orthorhombic(x.leq.0.4), psudo-cubic(x=0.5), and rhombohedral (x.geq.0.7) in turn, as the amount of LaAIO$_{3}$ increased. The dielectric constant and temperature coefficient of resonant frequency of solid solution were decreased with the content of LaAIO$_{3}$, whereas, the value of Q . f$_{o}$ was increased. The microwave dielectric material having Q . f$_{o}$ = 32, 500, .epsilon.$_{r}$ = 42, and .tau.$_{f}$ = 5 ppm/.deg. C was obtained from the 0.35CaTiO$_{3}$-0.65LaAIO$_{3}$ composition sintered at 1600.deg. C for 4hrs.hrs.hrs.

• Current Applied Physics
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• v.18 no.11
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• pp.1248-1254
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• 2018

Magnetization versus temperature and magnetic-field measurements, M(T, $H_a$), have been carried out to study the magnetic and critical properties of polycrystalline $La_{1-x}Ba_xCoO_3$ (x = 0.3 and 0.5) cobaltites. These compounds with the density of ${\sim}6.2g/cm^3$ crystallized in the $R{\bar{3}}c$ rhombohedral and $Pm{\bar{3}}m$ cubic structures, respectively. With an applied field $H_a=200Oe$, M(T) data have revealed that the samples with x = 0.3 and 0.5 exhibit the ferromagnetic-paramagnetic (FM-PM) phase transition at the Curie temperature points $T_C=202$ and 157 K, respectively. At 4.2 K, the saturation magnetization ($M_{sat}$) decreases from 35.9 emu/g for x = 0.3-26.1 emu/g for x = 0.5. Particularly, the critical-behavior analyses in the vicinity of $T_C$ reveal all samples undergoing a second-order phase transition, with critical exponent values (${\beta}=0.328$ and ${\gamma}=1.251$ for x = 0.3, and ${\beta}=0.331$ and ${\gamma}=1.246$ for x = 0.5) close to those expected for the 3D Ising model. This proves short-range magnetic order existing in $La_{1-x}Ba_xCoO_3$. We believe that magnetic inhomogeneities due to the mixture of hole-rich FM regions (confined in the trivalent-cobalt hole-poor anti-FM matrix) and uniaxial anisotropy prevent long-range order in $La_{1-x}Ba_xCoO_3$.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.439-444
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• 1996

0.15(B $a_{0.95}$ S $r_{0.05}$)O-0.15(S $m_{2(1-x}$/N $d_{2x}$) $O_{3}$-0.7Ti $O_{2}$(x=0-10[m/o]) ceramics were fabricated by mixed oxide method. Microwave dielectric properties were investigated with contents of N $d_{2}$ $O_{3}$. In the case of specimen with N $d_{2}$ $O_{3}$(6[m/o]), dielectric constant, quality factor and temperature coefficient of resonant frequency were 78.14, 2938(at 3[GHz]) and +14.19[ppm/.deg. C], respectively. By comparison its properties with undoped specimen, dielectric constant and quality factor were highly improved, but the temperature coefficient of resonant frequency was increased to positive value......

• Transactions on Electrical and Electronic Materials
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• v.11 no.3
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• pp.126-129
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• 2010

(1-X) $(Na_{0.5}K_{0.5})NbO_3-X$ $K_4CuNb_8O_{23}$ (NKN-X KCN) ceramics were produced using the conventional solid state sintering method, and their sinterability and electric properties were investigated. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCN content and the sintering temperature. In particular, the KCN addition to the NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 2.0 mol% sintered at $1,150^{\circ}C$ possesses the optimum properties (${\varepsilon}_r=241$, $d_{33}=78$, $k_p=0.34$ and $Q_m=1,121$). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.397-403
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• 2003

Microwave dielectric properties of (1-x)ZnW $O_4$-xTi $O_2$ ceramic systems were investigated with calcination temperatures and Ti $O_2$ contents. The ZnW $O_4$ ceramic could be suitably sintered at 1075$^{\circ}C$ and showed the dielectric constant of 13.6, quality factor(Q$\times$ $f_{O}$value) of 22,000 and temperature coefficient of resonant frequency($\tau$$_{f}$) of -65$\pm$2ppm/$^{\circ}C$. Increasing the amount of Ti $O_2$ in the range of 0.25 to 0.45 mol, the dielectric constant and $\tau$$_{f}$ increased due to the role of Ti $O_2$ but the quality factor decreased due to the increase of phase boundaries. The 0.7ZnW $O_4$-0.3Ti $O_2$ ceramic showed the dielectric constant of 19.8, qualify factor(Q$\times$ $f_{0}$) of 20,000 and $\tau$$_{f}$ of -3$\pm$1ppm/$^{\circ}C$.>.EX>.>.>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.300-301
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• 2007

$Mg_4(Nb_{2-x}V_x)O_9$ (MNV) ceramics have been prepared by a hydrothermal method. Low-temperature sintering of $Mg_4(Nb_{2-x}V_x)O_9$ (MNV) by V substitution for Nb was discussed in this study. A $Q{\cdot}f_0$ value of 103,297 GHz with a ${\varepsilon}_r$ of 12.56 and a ${\tau}_f$ of $-10.53\;ppm/^{\circ}C$ was obtained when x=0.0625 after sintering at $1100^{\circ}C$ for 5 h.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.5
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• pp.226-231
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• 2001

The $Mg_{1-x}Sr_xTiO_3\;(x=0.02{\sim}0.08)$ ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were $1250^{\circ}C{\sim}1350^{\circ}C$, 2hr., respectively. From the X-ray diffraction patterns, it was found that the perovskite $SrTiO_3$ and ilmenite $MgTiO_3$ structures were coexisted in the $Mg_{1-x}Sr_xTiO_3\;(x=0.02{\sim}0.08)$ ceramics. The dielectric constant( ${\epsilon}_r$) was increased with addition of $SrTiO_3$. The temperature coefficient of resonant frequency( ${\tau}_f$) was gradually varied from negative value to the positive value with increasing the $SrTiO_3$. The temperature coefficient of resonant frequency of the $Mg_{1-x}Sr_xTiO_3(x=0.036)$ ceramics was near zero, where the dielectric constant, quality factor, and ${\tau}_f$ were 20.65, 95120 and +1.3ppm/$^{\circ}C$, respectively.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.55-61
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• 2006

The microwave dielectric properties and low temperature sintering of $Ca[Ti_{1-x}(Ni_{1/3}Nb_{2/3})_x]O_3$ system were investigated at the sintering temperature $1,200\~1,350^{\circ}C$. The density and quality factors $(Q{\times}f)$ increased while dielectric constants slightly decreased with the decrease of Ti. The dielectric constant, quality factor, and temperature coefficient of resonance frequency $(\tau_f)$ were 64, 17,000 GHz, and $-9.1\;ppm/^{\circ}C$ respectively, when $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ ceramics were sintered at $1,300^{\circ}C$ for 4 h. $2Li_2O-B_2O_3$ was added to $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ to decrease the sintering temperature for LTCC application. The microwave dielectric properties of the samples sintered at $925^{\circ}C$ for 2 h with the addition of $6\;wt\%\;2Li_2O-B_2O_3$ were $\varepsilon_r=48.7,\;Q{\times}f=8,460\;GHz$, and $\tau_f=+5.6ppm/^{\circ}C$. Compatibility test of the composition with silver electrode shows no reaction with silver electrode, implying the feasibility as a high-K LTCC material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.196-199
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• 2000

Since the reports of CMR(colossal magnetoresistance) effects in some single crystal R-P phase $La_{1+x}Sr_{2-x}Mn_2O_7$, considerable researches have been carried out to find optimum composition and to understand the role of dimensionality in the CMR mechanism of this system. In this study, layered perovskite $Ln_xCa_{1-x}MnO_{4}$ (x=0.5, Ln=Pr, Nd, Sm, Gd) phases were synthesized by solid state reaction and their structures were refined by Rietveld method. Electrical and magnetic properties were measured between room temperature and liquid helium temperature and compared with those of two dimensional $La_{1.4}Sr_{1.6}Mn_2O_7$ phase.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.306-312
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• 1995

In order to know properties in rice starch during storage of rice, rice starch from stored rice(stored at $5^{\circ}C$, R.H. 65% and $30^{\circ}C$, R.H. 85%, for 16 weeks) used in this experiment. Water binding capacity of rice starch increased for 8 weeks, and then it decreased. As the storage period took longer, swelling power and solubility, optical transmittance, blue value, total amylose content and soluble amylose content decreased. For the same periods, changes in rice starch from stored rice$(30^{\circ}C$, R.H. 85%) were made more than those in rice starch at $5^{\circ}C$, R.H. 65%. The granule shape of rice starch, irrespective of storage periods and conditions, didn't make a significant difference. The relative crystallinity of the rice starch by X-ray diffraction didn't distinctly changed till the second week. But, at the fourth week, that by X-ray diffraction significantly decreased, and then slightly decreased. As the storage period took longer, gelatinization temperature, melting temperature and melting enthalpy measured by DSC got higher, but gelatinization enthalpy got lower. For the same storage period, gelatinization temperature, melting temperature, gelatinization enthalpy and melting enthalpy of rice starch stored at $30^{\circ}C$, R.H. 85% made changes more than those of rice starch stored at $5^{\circ}C$, R.H. 65% did.