• Proceedings of the Korean Vacuum Society Conference
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• 2003.02a
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• pp.202-202
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.116.2-116
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• 2002

• Proceedings of the Materials Research Society of Korea Conference
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• 2004.05a
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• pp.71-71
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• 2004

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.295-302
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• 2008

$TiO_2,\;ZrO_2$, and $SiO_2$ were added in the concentration of 1 - 3 wt.% to improve long-term stability for the $SnO2$ thick film gas sensor. Short-term sensor resistances up to 90 h were measured to investigate the stabilization time of initial resistance in air. Long-term resistance drifts in air and in gas to 5000 ppm methane for the sensors annealed at $750^{\circ}C$ for 1 h and continuously heated at an operating temperature of $400^{\circ}C$ were also measured up to 90 days at an interval of 1 day. The long-term drifts in methane sensitivity for the three metal oxide-doped $SnO2$ sensors are closely related to methane sensitivity level, catalytic activity, and long-term drift in sensor resistance in air. Those stabilities are mainly discussed in terms of oxidation state and catalytic activity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.477-480
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• 2010

In this study, we fabricate 3 wt% $Li_2CO_3$ doped $(Ba,Sr)TiO_3$ thick films on the Ag/Pd bottom electrode printed $Al_2O_3$ substrates for the LTCCs (low temperature co-fired ceramics) applications. From the X-ray diffraction analysis, 3 wt% $Li_2CO_3$ doped BST thick films on the Ag/Pd printed $Al_2O_3$ substrates, which sintered at $900^{\circ}C$, showed perovskite structure without any pyro phase. The dielectric properties of 3 wt% $Li_2CO_3$ doped BST thick films are measured from 1 kHz to 1 MHz. To investigate the electrical properties of 3 wt% $Li_2CO_3$ doped BST thick films, we employ the impedance spectroscopy. The complex impedance of 3 wt% $Li_2CO_3$ doped BST thick films are measured from 20 Hz to 1 MHz at the various temperatures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.4
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• pp.212-215
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• 2018

The phase evolution, microstructure, and microwave dielectric properties of $Ba(Mg_{0.5-2x}Y_{2x}W_{0.5-x}Ti_x)O_3$ (x = 0.005~0.05) ceramics sintered at $1,700^{\circ}C$ for 1h were investigated. All compositions exhibited a 1:1 ordered cubic perovskite structure. The field emission scanning electron microscopy image revealed a dense microstructure in all the compositions. As the value of x increased, the lattice parameter, dielectric constant, and quality factor increased. The temperature coefficient of resonant frequency changed from $-19.6ppm/^{\circ}C$ to $-5.9ppm/^{\circ}C$ with increasing x value. The dielectric constant, quality factor, and temperature coefficient of resonant frequency of $Ba(Mg_{0.40}Y_{0.10}W_{0.45}Ti_{0.05})O_3$ were 21.7, 132,685 GHz, and $-5.9ppm/^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.296-299
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• 2003

In this paper, $0.10Pb(Sb_{1/2}Sn_{1/2})O_3-0.25PbTiO_3-0.65PbZrO_3$ ceramics were fabricated by the mixed-oxide method. The sintering temperature and time were $1230^{\circ}C$ and 2[hr], respectively. The structural, dielectric and piezoelectric properties with addition of NiO were studied. The crystal structure of a specimen was rhombohedral. As a result of SEM, the average grain size were decreased with increasing the contents of NiO. But the grains of the specimens doped with 0.4wt% NiO were increased, due to deposits of excess NiO at grain boundaries in the liquid phase. Relative dielectric constant and dielectric loss of the specimen doped with 0.1wt% NiO were 701 and 0.026, respectively.

• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.52-57
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• 2016

Nanoporous-layer-covered TiO₂ nanotube arrays (Type II TNTs) were fabricated by two-step electrochemical anodization. For comparison, conventional TiO₂ nanotube arrays (Type I TNTs) were also prepared by one-step electrochemical anodization. Types I and II TNTs were detached by selective etching and then transferred successfully to a transparent F-doped SnO₂ (FTO) substrate by a sol-gel process. Both FTO/Types I and II TNTs allowed front side illumination to exhibit incident photon-to-current efficiencies (IPCEs) in the long wavelength region of 300 to 750 nm without the absorption of light by the iodine-containing electrolyte. The Type II TNT exhibited longer electron lifetime and faster charge transfer than the Type I TNT because of its relatively fewer defect states. These beneficial effects lead to a high overall energy conversion efficiency (5.32 %) of the resulting dye-sensitized solar cell.

• Journal of the Korean Chemical Society
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• v.31 no.3
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• pp.215-224
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• 1987

The electrical conductuctivity measurements have been made on polycrystalline samples of various compositions in the $MgO-TiO_2$ system from 600 to $1100^{\circ}C$ under $Po_2$'s of $10^{-8}\;to\;10^{-1}$atm. Plots of log ${\sigma}$ vs. 1/T at constant $Po_2$ are found to be linear with the inflections, and the activation energies are 1.94eV for the intrinsic range and 0.48eV for the extrinsic range, respectively. The log ${\sigma}$ vs. log $Po_2$ curves are found to be linear at constant temperature, and the conductivity dependences of $Po_2$ are closely approximated by ${\sigma}\;{\alpha}\;Po_2^{-1/6}$ for the extrinsic and ${\sigma}\;{\alpha}\;Po_2^{-1/4}$ for the intrinsic range, respectively. The dominant defects in this system are believed to be oxygen vacancy for the extrinsic and $Ti^{3-}$ interstitial for the intrinsic range. The conduction mechanisms in both the extrinsic and the intrinsic ranges are proposed by the results of the electrical conductivity dependence on the oxygen partial pressure. Polaron model was suggested in the extrinsic region by the conductivity dependences of temperature and $Po_2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.229-233
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• 2019

Pure $BiFeO_3$ (BFO) and (Eu, V) co-doped $Bi_{0.9}Eu_{0.1}Fe_{0.975}V_{0.025}O_{3+{\delta}}$ (BEFVO) thin films were deposited on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by chemical solution deposition. The effects of co-doping were observed by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). The electrical properties of the BEFVO thin film were improved as compared to those of the pure BFO thin film. The remnant polarization ($2P_r$) of the BEFVO thin film was approximately $26{\mu}C/cm^2$ at a maximum electric field of 1,190 kV/cm with a frequency of 1 kHz. The leakage current density of the co-doped BEFVO thin film ($4.81{\times}10^{-5}A/cm^2$ at 100 kV/cm) was two orders of magnitude lower than of that of the pure BFO thin film.