• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.8
• /
• pp.738-748
• /
• 2008

In this study, it has been investigated on the changing behavior of electrical properties in $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=2.0, 1.0 and 0.5) ceramics. The samples were prepared by conventional ceramic process, and then characterized by I-V, C-V curve plots, impedance and modulus spectroscopy (IS & MS) measurement. The electrical properties of ZBS systems were strongly dependent on Sb/Bi. In ZBS systems, the varistor characteristics were deteriorated noticeably with increasing Sb/Bi and the donor density and interface state density were increased with increasing Sb/Bi. On the other hand, we observed that the grain boundary reacted actively with the ambient oxygen according to Sb/Bi ratio. Especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature. Besides, the increased pyrochlore and $\beta$-spinel phase with Sb/Bi ratio caused the distributional inhomogeneity in the grain boundary barrier height and the temperature instability. To the contrary, the grain boundary layer was relatively homogeneous and more stable to temperature change and kept the system highly nonlinear at high Bi-rich phase contents.

• Proceedings of the KIEE Conference
• /
• 1989.11a
• /
• pp.119-121
• /
• 1989

The properties of Pb-doped Bi-Sr-Ca-Cu-O Super-conductors prepared by solidstate reaction have been studied. Zero resistance was attained at l03K for the sample sintered 845[$^{\circ}C$]for 264hours and it was depended upon sintering conditions. From XRD data low Tc phase and high Tc phase were observed and the volume fraction of high Tc phase increased with increase in sintering period. The grain size increased with increase in sintering temperature and time.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.929-931
• /
• 1999

BSCCO thin films have been fabricated by co-deposition at an ultralow growth rate using ion beam sputtering(IBS) method. Bi 2212 phase appeared in the temperature range of 750 and $795^{\circ}C$ and single phase of Bi 2201 existed in the lower region than $785^{\circ}C$. Whereas, ozone gas pressure dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with $T_c$(onset) of about 90 K and $T_c$(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as $CaCuO_2$ was observed in all of the obtained films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05b
• /
• pp.94-97
• /
• 2005

Bismuth high Tc superconducting thin films are fabricated via a co-deposition process by an ion beam sputtering with an ultra low growth rate, and sticking processing of the respective elements are evaluated. The sticking processing of bismuth element in bismuth high Tc superconducting thin film formation was observed to show a unique temperature dependence; it was almost a constant value of 0.49 below about $730^{\circ}C$ and decreased linearly over about $730^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, $Bi_2O_3$, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the bismuth phase formation in the co-deposition process.

• Journal of the Korean Ceramic Society
• /
• v.29 no.2
• /
• pp.101-106
• /
• 1992

Sintering behavior, distribution of dopant oxides and electrical properties in the ZnO-Bi2O3-CoO-Sb2O3 and ZnO-Bi2O3-CoO-Sb2O3-Cr2O3 systems were studied. The linear shrinkage of ZnO varistors from 850 to 950$^{\circ}C$ was related to the decomposition reaction (py\longrightarrowsp+Bi2O3) of the pyrochlore phase. In the distribution of the dopant oxides (CoO, Sb2O3, Cr2O3), Co distribute uniformly throughout the sample, the distribution of Sb coincided with small particles (spinel phase, Zn7Sb2O12), and Cr distributed very consistently with Sb. The increase in breakdown voltage, due to the addition of Cr2O3, was not only attributed to the decrease in the ZnO grain size but also to the solution of Cr2O3 in the spinel phase. The leakage current (80% V60 ${\mu}\textrm{A}$) was increased by the addition of Cr2O3.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.893-896
• /
• 2000

The SrBi$_2$Ta$_2$O$\sub$9/(SBT) thin films are deposited on Pt-coated electrode(Pt/TiO$_2$/SiO$_2$/Si) using RF sputtering method. The SBT thin films deposited on substrate at 400-500[$^{\circ}C$]. SBT thin film deposited on Pt-coated electrodes have the cubic perovskite structure and polycrystalline state. With increasing annealing temperature from 600[$^{\circ}C$] to 850[$^{\circ}C$], flourite Phase was crystalized to 650[$^{\circ}C$] and Bi-layered perovskite phase was crystalized above 700[$^{\circ}C$]. The maximum remanent polarization is 11.73 ${\mu}$C/cm$^2$at 500[$^{\circ}C$] of substrate temperature and 750[$^{\circ}C$] annealing temperature for 30min.

• Korean Journal of Materials Research
• /
• v.15 no.11
• /
• pp.683-689
• /
• 2005

The structural, piezoelectric and ferroelectric properties of $(1-x)(Bi_{0.5}Na_{0.5})TiO_3$ x=0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) ceramics were investigated. A gradual change in the crystal and microstructures with tile increase of $BaTiO_3$ (BT) concentration was observed. The $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) samples show unusual properties as ferroelectric relaxer materials. We observed a phase transition in BNT solid solutions with BT having normal ferroelectric phase transition. At room temperature, BNT presents a single phase without the morphotropic phase boundary (MPB). In the case of samples doped with $4\~8 mol\%$ BT, rhombohedral-tetragonal MPB was formed and the piezoelectric properties were improved.

• Ceramist
• /
• v.23 no.1
• /
• pp.101-109
• /
• 2020

In this study, the phase transition behaviors of lead-free (Na_1/2Bi_1/2TiO₃)_(1-x)-(BaTiO₃)_x (NBT-BT) are investigated by using Brillouin spectroscopy. The elastic properties, sound velocity and absorption coefficient of NBT-BT are characterized as a function of temperature along different crystallographic axes. The temperature dependences of the elastic constants of NBT-BT near the morphotropic phase boundary are determined for the first time. The unpoled NBT-BT single crystals exhibits the typical relaxor behaviors, presenting broad acoustic and dielectric anomalies. The application of electric field induced discontinuous changes in the elastic properties at ~110℃, which indicates field-induced phase transition occurred. The electric field also changes the dielectric constant from more relaxor-like to ferroelectric-like dielectric behavior.

• Ocean Systems Engineering
• /
• v.2 no.2
• /
• pp.137-145
• /
• 2012

Recent developments in underwater image recognition methods have received large attention by the ocean engineering researchers. In this paper, an improved bi-dimensional empirical mode decomposition (BEMD) approach is employed to decompose the given underwater image into intrinsic mode functions (IMFs) and residual. We developed a joint algorithm based on BEMD and Canny operator to extract multi-pixel edge features at multiple scales in IMFs sub-images. So the multiple pixel edge extraction is an advantage of our approach; the other contribution of this method is the realization of the bi-dimensional sifting process, which is realized utilizing regional-based operators to detect local extreme points and constructing radial basis function for curve surface interpolation. The performance of the multi-pixel edge extraction algorithm for processing underwater image is demonstrated in the contrast experiment with both the proposed method and the phase congruency edge detection.

• Proceedings of the KIEE Conference
• /
• 1991.07a
• /
• pp.201-203
• /
• 1991

T. Kanal et al, were studied the superconducting properties in Bi system by mechanical grinding, in which the authors found that the samples ground degraded from the superconducting phases to nonsuperconducting phases. To obtain more information of the practical application in Bi system with high-Tc phase in this paper, these samples mechanically ground and the high-Tc phase properties of grinding powder samples were investigated.