• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.63-69
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• 2017

In this work, two different platinum (Pt) counter electrodes have been prepared by spin coating a Pt solution and screen printing a Pt paste on fluorine doped tin oxide (FTO) glass substrate followed by sintering at $380^{\circ}C$ for 30 min. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) analyses of the Pt electrodes showed that the spin coated electrode was catalytically more active than the screen printed electrode. The above result agrees well with the surface morphology of the electrodes studied by atomic force microscopy (AFM) and the photovoltaic performance of the dye-sensitized solar cells (DSSCs) fabricated with the Pt electrodes. Moreover, calculation of current density-voltage (j-V) curves according to diode model with the parameters obtained from the experimental j-V curves and the EIS data of the DSSCs provided a quantitative insight about how the catalytic activity of the counter electrodes affected the photovoltaic performance of the cells. Even though the experimental situations involved in this work are trivial, the method of analyses outlined here gives a strong insight about how the catalytic activity of a counter electrode affects the photovoltaic performance of a DSSC. This work, also, demonstrates how the photovoltaic performance of DSSCs can be improved by tuning the performance of counter electrode materials.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.6
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• pp.799-807
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• 2006

The catalytic activity of $Pt/{\gamma}-Al_2O_3$ catalysts for the oxidation of toluene and toluene+xylene mixture was investigated in the microreactor of fixed-bed type. The calcination temperatures and loadings of $Pt/{\gamma}-Al_2O_3$ catalysts played the important role in the activity of catalysts for the oxidation of toluene. The increasing calcination temperatures and loadings of $Pt/{\gamma}-Al_2O_3$ catalysts increased the crystallite size of the platinum to result in the higher oxidation activity of catalysts. The catalytic activity for the toluene oxidation over $Pt/{\gamma}-Al_2O_3$ catalysts turned out to be increasing in the order of $500^{\circ}C\;<\;800^{\circ}C<600^{\circ}C\;<\;700^{\circ}C$ for calcination temperatures and 0.1 wt% < 0.3 wt% < 1.0 wt% for platinum loadings, respectively. The 1.0 wt% $Pt/{\gamma}-Al_2O_3$ catalysts calcined at $700^{\circ}C$ for 3 hrs in the air showed the highest activity for the oxidation of the toluene. The decrease of oxidation activity of $Pt/{\gamma}-Al_2O_3$ catalysts calcined at $800^{\circ}C$ might result from the decrease of active sites by sintering of platinum metals as well as ${\gamma}-Al_2O_3$ supports. The 1.0wt% $Pt/{\gamma}-Al_2O_3$ catalyst showed the activity from the lower temperature at $120^{\circ}C$, reached the light-off temperature ($T_{50%}$) at $180^{\circ}C$, and leveled off its activity at $340^{\circ}C$ with the conversion of 100% 'Mutual promotion' effects were observed for the binary mixture of toluene and xylene. The activity of the easy-to-oxidize toluene was slightly increased with the existence of the xylene. It might suggest the different mechanism for the oxidation of toluene and xylene on the $Pt/{\gamma}-Al_2O_3$ catalysts on different sites, and its reaction of gaseous oxygen.

• Journal of Sensor Science and Technology
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• v.6 no.5
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• pp.392-399
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• 1997

In this study, the effect of the sintering temperature on the dielectric and piezoelectric properties of 0.5 wt% $MnO_{2}$-doped $0.125Pb(Mg_{1/2}Nb_{2/3})O_{3}-0.435PbTiO_{3}-0.44PbZrO_{3}$ ceramics were investigated aiming at ultrasonic motor applications. From experimental result, it was found that the optimal sintering temperature condition was at $1270^{\circ}C$. The sample sintered at $1270^{\circ}C$ had density of $7.72\;g/cm^{3}$, dielectric constant of 570, dielectric loss of 0.82%, remanent polarization of $19.18{\mu}C/cm^{2}$, coercive field of 9.63 kV/cm, electromechanical coupling factor of radial mode of 55.1%, mechanical quality factor of 886. Temperature and frequency dependence of dielectric constant and dielectric loss of the sintered sample at $1270^{\circ}C$ was also investigated.

• Journal of the Korean Ceramic Society
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• v.30 no.8
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• pp.657-663
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• 1993

BaTiO3 sputtering targets of 3 inch diameter were prepared by sintering the CIP (Cold Isotatic Pressing) compacts at 136$0^{\circ}C$ for 3hrs. The apparent density and grain size were 97% and 30${\mu}{\textrm}{m}$, respectively. After BaTiO3 films were deposited on Si and Pt/Ti/SiO2/Si substrates using these targets, films were annealed at various conditions and the crystallization behavior, reaction with the substrate and the electrical properties were investigated. The films on both substrates required 5~20hrs furnace annealing for crystallization at the temperatures from $600^{\circ}C$ to 80$0^{\circ}C$. For the films on Si substrate, interaction between the film and the substrate was suppressed upt o $700^{\circ}C$ for 10 hrs and the relative dielectric constant was 30. As the annelaing temperature and time were increased, the relative dielectric constants of the films decreased due to the formation of silicate phases through the reaction with the substrate. For the BaTiO3 films on Pt/Ti/SiO2/Si substrate, the reaction with the substrate was further reduced when the annealing condition was identical to that for Si substrate, but the reaction between the layers in Pt electrode took place above $700^{\circ}C$. When the films were annealed at $600^{\circ}C$ where the stability of Pt electrode was sustained, relative dielectric constant was increased to 110 since the reaction with substrate was effectively reduced even for a longer annealing time and the crystallization was enhanced.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.407-411
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• 2022

Bulk-sized PbTiO₃ (PT), which is widely known as a high-performance ferroelectric oxide but cannot be fabricated into a monolithic ceramic due to its high c/a ratio, was successfully prepared with a high tetragonality by partially substituting Ni ions for Pb ions using a solid-state reaction method. We found that Ni-doped PT was well-fabricated as a bulk monolith with a significant c/a ratio of ~1.06. X-ray diffraction on as-sintered and crushed samples revealed that NiTiO₃ secondary phase was present at the doping level of more than 2 at.%. Scanning electron microscopic study showed that NiTiO₃ secondary phase grew on the surface of PT specimens regardless of the doping level possibly due to the evaporation of Pb during sintering. We demonstrated that an unconventional introduction of Ni ions into A-site plays a key role on the fabrication of bulk PT, though how Ni ion functions should be studied further. We expect that this study contributes to a further development of displacive ferroelectric oxides with a high c/a ratio.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.335-337
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• 1995

In this study, $Pb(Zr_{0.52}Ti_{0.48})O_3$ ceramic thin films were fabricated from an alkoxide-based by Sol-Gel method. $Pb(Zr_{0.52}Ti_{0.48})O_3$ stock solution was made and spin-coated on the $Pt/SiO_2/Si$ substrate at 4000[rpm] for 30[sec]. Coated specimens were dried at 400[$^{\circ}C$] for 10 [min]. The coating process was repeated 4 times and then heat-treated at 500$\sim$800[$^{\circ}C$], 1 hour. The final thickness of the thin films were about 3000[A]. The crystallinity and microstructure of the thin films were investigated for varing the sintering condition. The ferroelectric perovskite' phases precipitated under the sintering of 700[$^{\circ}C$] for 1 hours. In the $Pb(Zr_{0.52}Ti_{0.48})O_3$ thin films sintered at 700[$^{\circ}C$] for 1 hour, dielectric constant and dielectric loss were 2133, 2.2[%] at room temperature, respectively. $Pb(Zr_{0.52}Ti_{0.48})O_3$ thin film capacitors having good dielectric and electrical properties are expected for the application to the dielectric material of DRAM.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.204.2-204.2
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• 2014

Among various metal oxides, ZrO2 is of particular interests and has received widespread attention thanks to its ideal mechanical and chemical stability. As a cheap metal, Ag nanoparticles are also widely used as catalysts in ethylene epoxidation and methanol oxidation. However, the nature of Ag-ZrO2 interfaces is still unknown. In this work, the growth, interfacial interaction and thermal stability of Ag nanoparticles on ZrO2(111) film surfaces were studied by low-energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES), and X-ray photoelectron spectroscopy (XPS). The ZrO2(111) films were epitaxially grown on Pt(111). Three-dimensional (3D) growth model of Ag on the ZrO2(111) surface at 300 K was observed with a density of ${\sim}2.0{\times}1012particles/cm2$. The binding energy of Ag 3d shifts to low BE from very low to high Ag coverages by 0.5 eV. The Auger parameters shows the primary contribution to the Ag core level BE shift is final state effect, indicating a very weak interaction between Ag clusters and ZrO2(111) film. Thermal stability experiments demonstrate that Ag particles underwent serious sintering before they desorb from the zirconia film surface. In addition, large Ag particles have stronger ability of inhibiting sintering.

• Journal of Sensor Science and Technology
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• v.18 no.5
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• pp.343-348
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• 2009

$NiO{\cdot}(Co_{0.25}Mn_{0.75})_2O_3$(Mn-Ni-Co) and $Ba_{0.5}Sr_{0.5}TiO_3$(BST) thick films were screen printed on Pt patterned alumina substrate to investigate the effects of sintering temperature on humidity and temperature sensing properties of ceramic sensors. A raise in sintering temperature increased resistance and B constant of the Mn-Ni-Co temperature sensor. This may have derived from the synergic effects of the reduction in charge carriers caused by the substitution of Co for Mn as well as the formation of microcracks from the difference in thermal expansion coefficients. Dependence of resistance on humidity of the Mn-Ni-Co temperature sensor, however, was not found. BST films sintered at temperatures in the range of $1100^{\circ}C$ to $1150^{\circ}C$ showed excellent humidity sensing properties. The BST humidity sensor was faster in its response than the Mn-Ni-Co temperature sensor. The humidity sensor, however, proved to be unstable under various temperatures, suggesting a need for a temperature stabilizing device. In contrast, the Mn-Ni-Co temperature sensor was stable under humid conditions.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.91-93
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• 1989

x $Pb(Sb_{1/2}Sn_{1/2})O_3-PbTiO_3-PbZrO_3$, (0.05$\leq$x$\leq$0.30) ternary compound ceramics were fabricated by the mixed oxide method. The sintering temperature and time were $1200{\sim}1300[^{\circ}C]$, 2 hour, respectively. Increasing the PSS contents, the transition temperatures were decreased. The relative dielectric constant and Curie temperature of the 0.30PSS-0.20PT-0.50PZ specimens were 372, 190[$^{\circ}C$]. The pyroelectric coefficient, figure of merits for pyroelectric current and detectivity of the 0.25PSS-0.25PT-0.50PZ specimens had the good values, $5.41{\times}10^{-8}[C/cm^{2}K]$, $27.72{\times}10^{-12}[Ccm/J]$, $7.65{\times}10^{-10}{Ccm/J]$, respectively.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.934-942
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• 1990

The quarternary system ceramics 0.5[yPb(Zn1/3Nb2/3)O3-(1-y)Pb(Ni1/3Nb2/3)O3]-0.5[xPbTiO3-(1-x)PbZrO3](PZN-PNN-PT-PZ) was fabricated by the columbite precursor method to obtain a stabilized perovskite structure and by conventional method to evaluate the efficiency of the former methd. Dielectric and piezoelectric properties were investigated and the stability of the perovskite phase was studied as a function of PZN and PT contents and firing temperature. In the samples prepared by the columbite precursor method, the pyrochlore phase, which is detrimental to both the dielectric and piezoelectric properties, was not observed in the absence of PZN, and electric properties were improved even when fabricated at low temperature. By adding PZN, some pyrochlore phase appeared and the morphotropic phase boundary of the samples shifted to more Zr-rich composition. The temperature dependence of piezoelectric constant decreased with the addition of PZN, due to the rising of the Curie point.