• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.839-846
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• 1996

Epitaxial (La, Sr)$CoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$by pulsed laser deposition for ferroelectric field effect transistor. Epitaxial $LaCoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$ heterostructures exhibited 70$\mu C/cm^2$ and 17 $\mu C/cm^2$at a positively and negatively poled states, respectively. On the other hand, epitaxial (La, Sr)$CoO_3/Pb(Zr,\;Ti)O_3/LaCoO_3$heterostructures show the remnant polarization states opposite to the $LaCoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$ heterostructures. This indicates that the interface between (La, Sr)$CoO_3$ (LSCO) and $Pb(Zr, Ti)O_3(PZT)$ layers affects the asymmetric polarization remanence through electrochemical nature. The resistivity of $LaCoO_3$ (LCO) layer was found to be dependent on an ambient oxygen, primarily the ambient oxygen pressure during deposition. The resistivity of the LCO layer varied in the range of 0.1-100 $\Omega$cm. It is suggested that, with an appropriate resistivity of the LCO layer, the LCO/PZT/LSCO heterostructure can be used as the ferroelectric field effect transistor.

• Journal of Powder Materials
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• v.18 no.2
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• pp.149-158
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• 2011

Electro-Discharge Sintering (EDS) employs a high-voltage/high-current-density pulse of electrical energy, discharged from a capacitor bank, to instantaneously consolidate powders. In the present study, a single pulse of 0.57-1.1 kJ/0.45 g-atomized spherical $Ti_{52}Zr_{28}Ni_{20}$ powders in size range of 10~30 and $30\sim50{\mu}m$ consisting of ${\beta}$-(Ti, Zr) and icosahedral phases were applied to examine the structural evolution of icosahedral phase during EDS. Structural investigation reveals that high electrical input energy facilitates complete decomposition of icosahedral phase into C14 laves and ${\beta}$-(Ti, Zr) phases. Moreover, critical input energy inducing decomposition of the icosahedral phase during EDS depends on the size of the powder. Porous Ti and W compacts have been fabricated by EDS using rectangular and spherical powders upon various input energy at a constant capacitance of $450{\mu}F$ in order to verify influence of powder shape on microstructure of porous compacts. Besides, generated heat (${\Delta}H$) during EDS, which is measured by an oscilloscope, is closely correlated with powder size.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.193-195
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• 1994

In this study, the structural, dielectric and piezoelectrical properties of $xPb(Mg_{1/2}W_{1/2})O_3-(1-x)[0.41Pb(Ni_{1/3}Nb_{2/3})O_3-0.36PbTiO_3-0.23P Zr)_3]$ (x=0, 0.01, 0.02, 0.03, 0.04, 0.05) system ceramics were investigated. The dielectric constant ${\varepsilon_{33}}^{\tau}$ at loon temperature increased up to 3mol% PMW and decreased with further PMW content. The specimen with 1mol% $Pb(Mg_{1/2}W_{1/2})O_3$, which has the ${\varepsilon_{33}}^{\tau}=5509$, kp=59[%] and $d_{33}=758{\times}10^{-12}[C/N]$, exhibits good characteristics.

• Journal of the Korean Magnetics Society
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• v.10 no.2
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• pp.54-61
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• 2000

The structural and magnetic properties of sputtered CoNbZr alloy films were investigated. In the as-deposited $Co_{87.0}$N $b_{8.5}$Z $r_{4.5}$ film deposited at 2 mTorr and 130 W, we observed the minimum coercivity of 1.75 Oe, the maximum resistivity of 3000 $\mu$Ω.cm and permeability of 1095 at 100 MHz. As the Ar pressure or the RF input power increased, the permeability of films at 100 MHz decreased and the coercivity increased because of the development of columnar structure and the formation of unstable amorphous phase. Permeability lower than 100 and coercivity of 60 Oe were observed in film deposited at 1 mTorr or 190 W due to the formation of crystalline phase. Magnetic anisotropy field of as-deposited films could be reduced by rotating field annealing for 120 minutes at 30$0^{\circ}C$. After the annealing, the anisotropy field (Hk) decreased from 1.43 Oe to 0.3 Oe and the permeability increased from 1095 to 1345 because defects in as-deposited films were eliminated by the annealing.aling.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.1
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• pp.19-26
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• 2004

The growth of solid particles in TiC-XC-2vo1.% and TiC-XC-30vo1.% Ni alloys, (where X=Zr, W or Mo) was fitted to the equation of the form $d^3$-${do}^3$=Kt during the liquid phase sintering at 1,673K. Also, the grain growth behavior decreased markedly with the addition of ${MO}_2$C or WC and increased with the addition of zrC. The contiguity was greater in the alloys with a smaller growth rate constant and especially, decreased by increasing the Ni content in the TiC-${MO}_2$C-Ni alloy. In addition, the effect of the addition of carbide on the grain growth of 2 vo1.% Ni alloys was found to be similar to that of 30vo1.% Ni alloys. Consequently, the grain growth mechanism cannot be explained by the usual solution / reprecipitation process, but can be explained in terms of a new growth velocity equation, which includes the effects of contiguous carbide grain boundaries in restricting the overall grain growth, as well as the area of the solid / liquid interface in the alloy.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.1
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• pp.60-68
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• 2011

[ $ZrO_2-TiO_2$ ]binary oxides with various Zr:Ti molar ratios were prepared by sol-gel method and Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membranes were fabricated for proton exchange membrane fuel cells (PEMFCs) at high temperature and low humidity. Water uptake, Ion exchange capacity (IEC), and proton conductivity of Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membranes were characterized and these composite membranes were tested in a single cell at $120^{\circ}C$ with various relative humidity (R.H.) conditions. The obtained results were compared with the unmodified membranes (Nafion$^{(R)}$ 112 and Recast Nafion$^{(R)}$). A Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membrane with 1:3 of Zr:Ti molar ratio showed the highest performance. The performance showed 500 mW/$cm^2$ (0.499V) at $120^{\circ}C$, 50% R. H., and 2 atm.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.457-468
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• 1993

In oxide matrix-SiC(W) composites, instability and glassy phase formation due to oxidation at the high temperature and the diffusion of Si, respectively, cause brittle fracture and low reliability for ceramic materials. The mode of contribution in each mechanisms induced by matrix-whisker debonding, varies with the morphology of matrix-whisker interfaces. This work has described the dispersion behaviours and stabilization mechanisms in slip systems, and multiple toughening mechanisms by dint of two second phase different from each other when spherical ZrO2 and chemically stable Al2O3(W) is respectively added in Al2O3 matrix. To obtain complexshaped components, slip casted bodies were sintered at 1$600^{\circ}C$, 2hrs up to 98~99% R.D.. Multiple toughening mechanisms in comparison with theories reported until now will be discussed as a result of the phase analysis of ZrO2 by athermal behaviours and microstructural characterizations as well as measured mechanical properties.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.494-496
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• 2000

The properties of piezoelectric and dielectric for 0.05Pb$(Mn_{0.4}W_{0.2}Nb_{0.4})O_3$ - $0.95PbZr_{x}Ti_{1-x}O_{3}$ compositions have been investigated. In the composition of 0.05Pb$(Mn_{0.4}W_{0.2}Nb_{0.4})O_3$-$0.95PbZr_{0.51}Ti_{0.49}O_{3}$, the values of $k_p$ and ${\varepsilon_{33}}^T/{\varepsilon}_0$ are maximized, but $Q_m$ was minimized ($k_p$=56.5[%], $Q_m$=1130, $d_{33}$=258[pC/N], ${\varepsilon_{33}}^T/{\varepsilon}_0$=1170). The grain size was suppressed and the uniformity of gram was improved at the $1100[^{\circ}C]$. Dielectric constant increase at the Ti rich, but decrease at the Zr rich after poling. Because the dielectric constant after poling is determined by compromising effects between dipole switching and electostriction inducing stress(dielectric constant increasing factor) and dipole rotation to the poling direction (dielectric constant decreasing factor).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.272-276
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• 2001

Multicomponent $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ bulk matallic glass alloy shows good bulk glass forming ability due to its high resistance to crystallization in the undercooled liquid state.1) In this study, DSC and X-ray diffractometry have been performed to confirm the amorphous structure of the master $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy. To investigate the mechanical properties and deformation behaviors of the bulk metallic $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy, a series of compression tests has been carried out at the temperatures ranging from $351^{\circ}C$ to $461^{\circ}C$ and at the various initial strain rates from $2{\times}10^{-4}s^{-1}\;to\;2{\times}10^{-2}s^{-1}$. There are two types of nominal stress-strain curves. The one shows linear stress-strain relationship meaning fracture at maximum stress, the other shows plastic deformation including steady-state flow. Also DSC analysis for the compressed specimens has been performed to investigate the change of thermal stability and crystallization behavior for the various test conditions.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.652-659
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• 1996

Sintering characteristics and electrical properties of xPb(Mg$_{1}$8/Te$_{1}$8/Mn$_{1}$4/Nb$_{1}$2/) $O_{3}$-(1-x) Pb (Zr$_{1}$2/ $Ti_{1}$2/) $O_{3}$ (x=0.075, 0.1, 0.125) ceramics are investigated. A sintering temperature of ceramics could be reduced to 950.deg. C by a reaction between PbO and B site compound material. The physical properties of 0.1Pb(Mg, Te, Mn, Nb) $O_{3}$ - 0.9Pb(Zr, Ti) $O_{3}$ bulk ceramic with 3wt% glass frit(0.857PbO-0.143W $O_{3}$) were following : den = 7.95 g/cm$^{3}$, T$_{c}$=340.deg. C, .epsilon.$_{33}$= 754, k$_{31}$=0.3 and Q.=1780. The 3-layer piezoelectric transformer by using a tape casting method showed a good monolithic structure, and its voltage setup ratio was 2.5 times higher than that of a single device by using bulk ceramics.s.s.