• 한국전자파학회논문지
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• 제15권9호
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• pp.826-834
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• 2004

본 논문에서는 소형이며 광대역 특성을 가지는 안테나를 위해 Bi$_2$O$_3$가 첨가된 BaTi$_4$$O_{9}$ 세라믹스를 이용하여 후막 모노폴 안테나를 제작하였다. 그 결과 첨가된 Bi가 치환되어 이차상인 Bi$_4$Ti$_3$O$_{12}$를 형성되었고 이에따라 높은 비유전율은 일정하였고 품질계수(Q$_{f}$${\times}$f)는 급격히 감소하였다. 안테나 특성에 있어서 비유전율보다는 품질 계수의 영향을 직접적으로 받았다. 대역폭을 측정한 결과 Bi$_2$O$_3$ 첨가량이 증가할수록 급격한 품질계수 감소와 함께, 대역폭은 16 %에서 33 %로 증가하였다. 이에 반하여 이득은 -0.8 dBi에서 -4.3 dBi로 감소하였다. 이로인해 방사 패턴은 Bi$_2$O$_3$ 미(未)첨가시 보다 낮은 dBi 값을 보여 주었다. 특히 방사 패턴을 측정 한 결과 무 지향성을 보여야 될 x-y면 방사 패턴의 경우 격자구조의 왜곡으로 인한 파장의 산란과 공기와 유전체의 경계면에서 높은 비유전율의 차이로 굴절이 일어나 심하게 왜곡되어 있었다. 그러나 낮은 품질계수로 인하여 모든 조성 범위에서 우수한 -10 dB 대역폭 특성을 보여주었다.주었다..

• 한국표면공학회지
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• 제51권6호
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• pp.365-371
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• 2018

1D core-shell nanostructures have attracted great attention due to their enhanced physical and chemical properties. Specifically, oriented single-crystalline $TiO_2$ nanorods or nanowires on a transparent conductive substrate would be more desirable as the building core backbone. However, a facile approach to produce such structure-based hybrids is highly demanded. In this study, a three-step hydrothermal method was developed to grow NiMn-layered double hydroxide-decorated $TiO_2$/carbon core-shell nanorod arrays on transparent conductive fluorine-doped tin oxide (FTO) substrates. XRD, SEM, TEM, XPS and Raman were used to analyze the obtained samples. The in-situ fabricated hybrid nanostructured materials are expected to be applicable for photoelectrode working in water splitting.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1119-1121
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• 1993

The PSN-PT-PZ ceramics doped with the Mn-oxide(0.5wt%) were fabricated by the mixed oxide method at 1250($^{\circ}C$) for 2(hr) and then the dielectric and pyroelectric properties were investigated with the compositions. In the 0.05PSN-0.4PT-0.55PZ specimen with 0.5(wt%) $MnO_2$, the pyroelectric coefficient was $6.6{\times}10^{-8}(C/Cm^2^{\circ}C)$, and the figure of merits for pyroelectric current and voltage were $27{\times}10^{-9},\;45{\times}10^{-12}$(C.Cm/J), respectibly.

• 한국세라믹학회지
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• 제42권6호
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• pp.443-447
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• 2005

Fracture behavior was investigated in the $Al_2O_3-TiO_2(3 wt{\%})-LaPO_4(25 wt{\%}$) composite ceramics. To improve the fracture toughness of alumina ceramics, $TiO_2$ and $LaPO_4$ as a second phase were introduced. The samples were made by conventional powder processing method. Green compacts were sintered at $1600^{\circ}C$ for 2 h in air. Fracture toughness was tested using Indentation Strength Bending(ISB) method. From the bending test, enhanced fracture toughness was found in the composite, compared to the pure and $TiO_2$-doped alumina. The main factor of the enhancement of fracture toughness seems to be attributed to the weak interphase role of the $LaPO_4$ as a particulate type.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2295-2298
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• 2014

To effectively destruct 2-chlorophenol, a representative sterile preservative, nanometer-sized Mn (0.5, 1.0, 3.0 mol %)-incorporated $TiO_2$ powders were synthesized by a solvothermal method. XRD result demonstrated that the Mn ingredients were perfectly inserted into $TiO_2$ framework. The Mn-$TiO_2$ particles exhibited an anatase structure with a particle size of below 20 nm. The absorbance was shifted to the higher wavelength on Mn-$TiO_2$ compared to that of $TiO_2$. Otherwise, the PL intensities which has a close relationship for recombination between holes and electrons significantly decreased on Mn-$TiO_2$. The photodecomposition for 2-chlorophenol in a liquid system was enhanced over Mn-doped $TiO_2$ compared with pure $TiO_2$: 2-chlorophenol of 50 ppm was completely decomposed after 12 h when 1.0 mol % Mn-$TiO_2$ was used. Consequently, the core of this paper is as follows. introducing Mn into $TiO_2$ framework reduced the band-gap, moreover, it played as an electron capture resulted to lower recombination between electrons and holes during photocatalytic reaction for removal of 2-cholophenol.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.42.2-42.2
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• 2011

$TiO_2$ films were modified by adding a glass frit as a light scattering particle and applied to an anode electrode in dye-sensitized solar cells (DSSCs) to enhance the adhesion between $TiO_2$ and fluorine doped transparent oxide (FTO). Low melting point glass frits at contents of (3 to 7wt%) were added to the nano crystalline $TiO_2$ films. The light scattering properties, photovoltaic properties and microstructures of the photo electrodes were examined to determine the role of the low glass transition temperature ($T_g$) glass frit. Electrochemical impedance spectroscopy, Brunauer-Emmett-Teller method and scratch test were conducted to support the results. The DSSC with the $TiO_2$ film containing 3wt% low Tg glass frit showed optimal performance (5.1%, energy conversion efficiency) compared to the $TiO_2$-based one. The photocurrent density slightly decreased by adding 3wt% of the frit due to its large size and non conductivity. However, the decrease of current density followed by the decrease of electron transfer due to the large frit in $TiO_2$ electrode was compensated by the scattering effect, high surface area and reduced the electron transfer impedance at the electrolyte-dye-$TiO_2$ interface. The stability of the photo electrodes was improved by the frit, which chemically promoted the sintering of $TiO_2$ at relatively low temperature ($450^{\circ}C$).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.259-259
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• 2011

염료감응형 태양전지(Dye-Sensitized Solar Cells:DSSC)는 환경 친화적이며, 저가의 공정에 대한 가능성으로 기존의 고가의 결정질 실리콘 태양전지의 경제적인 대안으로 각광을 받고 있다. 최근 염료감응형 태양전지는 투명 전도성 산화막(Transparent Conducting Oxide : TCO)으로 사용되는 Fluorine Tin Oxide (FTO)가 증착된 유리기판 위에 주로 제작된다. FTO는 낮은 비저항과 가시광선 영역에서 높은 투과도를 가지는 우수한 전기-광학적 특성을 갖지만, 비교적 공정이 까다로운 Chemical Vapor Deposition (CVD)법으로 제조하며, 전체 공정비용의 60%를 차지하는 높은 생산단가로 인해 현재 FTO를 대체할 재료개발 연구가 활발히 진행되고 있다. 그 중 ZnO (Zinc Oxide)는 우수한 전기-광학적 특성과 비교적 저렴한 가격으로 새로운 TCO로써 주목받고 있다. ZnO는 넓은 energy band gap (3.4 [eV])의 육방정계 울자이트(hexagonal wurtzite) 결정 구조를 가지는II-VI족 n형 반도체 물질이며, III족 금속원소인 Al, Ga 및 In 등의 불순물을 첨가하면 TCO로서 우수한 전기-광학적 특성과 안정성을 나타낸다. 이들 물질중 $Zn^{2+}$ (0.060 nm)의 이온반경과 유사한 $Ga^{2+}$0.062 nm) 이온이 ZnO의 격자반경을 최소화 시킬 수 있다는 장점으로 최근 주목 받고 있다. 하지만 Ga-doped ZnO (GZO)의 경우 DSC에 사용되는 루테늄 계열의 산성 염료 하에 장시간 두면 표면이 파괴되는 문제가 발생하며, $TiO_2$ paste를 Printing 후 열처리하는 과정에서도 박막의 파괴가 발생할 수 있다. 이를 방지하기 위해 $TiO_2$ Blocking Layer를 GZO 투명전극 위에 증착하였다. 또한, $TiO_2$ Blocking Layer를 적용한 GZO 박막을 전면전극으로 이용하여 DSC를 제작하여 효율을 확인하였다. 2wt%의 $Ga_2O_3$가 도핑된 ZnO 박막은 20mTorr 400$^{\circ}C$에서 Pulsed Laser Deposition (PLD)에 의해 성장되었고, $TiO_2$박막은 Ti 금속을 타겟으로 이용하여 30mTorr 400$^{\circ}C$에서 증착되었다. Scanning electron microscopy (FE-SEM)을 이용한 박막 분석 결과 $TiO_2$가 증착된 GZO 박막의 경우 표면 파괴가 일어나지 않았다. Solar Simulator을 이용하여 I-V특성 측정결과 상용 FTO를 사용한 DSC 수준의 효율을 나타내었다. 이에 따라 Pulsed Laser Deposition을 이용해 제작된 GZO 기판은 $TiO_2$ Blocking Layer를 이용하여 표면 파괴를 방지할 수 있었으며, 이는 향후 염료감응형 태양전지의 투명전극에 적용 가능 할 것으로 판단된다.

• Journal of Magnetics
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• 제11권1호
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• pp.12-15
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• 2006

Magnetic and electronic properties of reduced rutile titanium dioxide $(TiO_{2-\delta})$ thin films doped by Mn have been investigated. The present sol-gel-grown semiconducting $TiO_{2-\delta}:Mn$ films exhibit a ferromagnetic behavior at room temperature for a limited range of Mn content. The Mn-doped films have p-type electrical conductivity with the carrier concentration near $10^{19}\;cm^{-3}$. The observed room-temperature ferromagnetism is believed to be intrinsic but not related to free carriers such as holes. Oxygen vacancies are likely to contribute to the room-temperature ferromagnetism-trapped carriers in oxygen vacancies can mediate a ferromagnetic coupling between neighboring $Mn^{+3}$ ions. The energy band-gap change due to the Mn doping measured by spectroscopic ellipsometry exhibits a red-shift compared to that of the undoped sample at low Mn content. It is explainable in terms of strong spin-exchange interactions between Mn ion and the carrier.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.255-259
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• 1999

The effects of $SiO_2$ and MnO addition on the sinterability and the electrical properties of 0.4mol% Nb-doped SrTiO3 varistor were investigated. The $SiO_2$ content was fixed at 0.3mol% and the MnO content varied from 0 to 1.0mol%. With 0.3 mol% $SiO_2$ and 0.3 mol% MnO addition, optimum density was obtained by sintering at $1200^{\circ}C$ without excess liquid phase. Impedance spectroscopy was performed on the sintered specimens with 0.3 mol% $SiO_2$ and various MnO contents. It was found that the resistivities of grains was increased with increasing MnO content. The dielectric constant was measured to be above 50000 in the specimen with 0.3~1.0mol% Mn content. The non-linear coefficient increased substantially with MnO addition, and it varied from 1 to 9 depending on the MnO content.

• 한국표면공학회지
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• 제52권6호
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• pp.306-309
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• 2019

Titanium (Ti) doped indium oxide (In₂O₃) films were deposited on glass substrates by RF magnetron sputtering and the films were rapid thermal annealed at 100, 200, and 300℃, respectively to investigate the influence of the rapid annealing on the opto-electrical performance of the films. The grain size of In₂O₃ (222) plane increased with annealing temperatures and their electrical resistivity decreased to as low as 8.86×10^-4 Ωcm at 300℃. The visible transmittance also improved from 77.1 to 79.5% when the annealing temperature increased. The optical band gap of the TIO films shifted from 4.010 to 4.087 eV with increases in annealing temperature from room temperature to 300℃. The figure of merit shows that the TIO films annealed at 300℃ had better optical and electrical performance than the other films prepared using lower-temperature or no annealing.