• Progress in Superconductivity
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• 제9권1호
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• pp.85-90
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• 2007

Lanthanum aluminate($LaAlO_3$) film has been prepared on single crystal and metal substrates by dip coating method. Lanthanum acetate and aluminum were prepared via ligand exchange starting from lanthanum nitrate hexahydrate and aluminum nitrate hexahydrate in acetate glacial acetic acid solution after being refluxed. Coating solution was obtained by diluting the gel with methanol and 2-methoxyethanol to adjust the total cation concentration to 0.67 M. Precursor coated film was prepared by dip-coating with a speed of 25 mm/min on various substrates such as $LaAlO_3$ (001), MgO(001), $SrTiO_3$(001) single crystal, LMO/MgO/Ni-alloy. Thin films have been obtained by heat treating the precursor film at various temperatures from $600^{\circ}C{\sim}900^{\circ}C$ and various heating rate from $0.83^{\circ}C/min{\sim}1.25^{\circ}C/min$ under $Ar/O_2$ mixture containing 1000ppm oxygen. The films have been characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD). XRD analysis for the prepared film showed that $LaAlO_3$ thin films with a preferred orientation of (100) plane parallel to substrate surface were obtained at $800^{\circ}C(1.11\;^{\circ}C/min)$ on LMO/MgO/Ni-alloy substrate, but the intensity decreased with the increase of heat treatment temperature.

• Progress in Superconductivity
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• 제9권1호
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• pp.102-106
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• 2007

YBCO films have been synthesized using a spray pyrolysis method. We used nitrates of Y, Ba, Cu as precursors. Deposition was made on $LaAlO_3$ (100) single crystal substrate by spraying the mist of aqueous precursor solution generated by a concentric nozzle. The distance between concentric nozzle and substrate was 15 cm. C-axis oriented films were obtained at deposition temperature of $740{\sim}800^{\circ}C$ and working pressure of 20 Torr. Oxygen partial pressure was 3 Torr and substrate was transported with the speed ranging from 0.23 cm/min to 0.7 cm/min by reel to reel. Scanning electron microscope (SEM) and X-ray diffraction (XRD) observation revealed that films are smooth and highly textured with (001) planes parallel to substrate. Highest critical current density (Jc) was $1.38\;MA/cm^2$ at 77K and self-field for the film with a thickness of $0.5\;{\mu}m$ prepared at a substrate temperature of $780^{\circ}C$ and $PO_2\;=3\;Torr$. The effect of temperature on the microstructure and YBCO phase formation will be discussed.

• 한국재료학회지
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• 제21권1호
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• pp.67-71
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• 2011

La doped CuO-ZnO-$Al_2O_3$ powders are prepared by sol-gel method with aluminum isopropoxide and primary distilled water as precursor and solvent. In this synthesized process, the obtained metal oxides caused the precursor such as copper (II) nitrate hydrate and zinc (II) nitrate hexahydrate were added. To improve the surface areas of La doped CuO-ZnO-$Al_2O_3$ powder, sorbitan (z)-mono-9-octadecenoate (Span 80) was added. The synthesized powder was calcined at various temperatures. The dopant was found to affect the surface area and particle size of the mixed oxide, in conjunction with the calcined temperature. The structural analysis and textual properties of the synthesized powder were measured with an X-ray Diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller surface analysis (BET), Thermogravimetry-Differential Thermal analysis (TG/DTA), $^{27}Al$ solid state Nuclear Magnetic Resonance (NMR) and transform infrared microspectroscopy (FT-IR). An increase of surface area with Span 80 was observed on La doped CuO-ZnO-$Al_2O_3$ powders from $25m^2$/g to $41m^2$/g.

• 한국전기전자재료학회논문지
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• 제33권3호
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• pp.214-218
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• 2020

In this study, Mg_xZn_1-xO thin films, which can be applied not only to active layers of light-emitting devices (LEDs), such as UV-LEDs, but also to solar cells, high mobility field-effect transistors, and power semiconductor devices, are fabricated using the sol-gel method. ZnO and Mg_0.3Zn_0.7O solution synthesized by the sol-gel method and the thin film were grown by spin coating on a Si (100) substrate and sapphire substrate. The solutions are synthesized by dissolving precursor materials in 2-methoxyethanol (2-ME) solvent, and then monoethanolamine (MEA) was added to the mixed solution as a sol stabilizer. Zinc acetate dihydrate is used as a ZnO precursor, while Mg nitrate hexahydrate and Mg acetate tetrahydrate are used as an MgO precursor. Then, the optical and structural characteristics of the fabricated thin films are compared. The molar concentration of the Zn precursor in the solvent is fixed at 0.3 M, and the amount of the Mg precursor is 30% of Mg²⁺/Zn²⁺. The optical characteristics are measured using an UV-vis spectrophotometer, and the transmittance of each wavelength is measured. Structural characteristics are measured using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Composition analyses are performed using energy dispersive X-ray spectroscopy (EDS). The Mg_0.3Zn_0.7O thin film was well formed at the ratio of the Mg precursor added regardless of the type of Mg precursor, and the c-axis of the thin film was decreased, while the band gap was increased to 3.56 eV.

• 마이크로전자및패키징학회지
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• 제20권1호
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• pp.33-37
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• 2013

전구체의 농도가 ZnO 나노로드의 성장에 미치는 영향에 대하여 알아보았다. ZnO 나노로드는 수열합성법에 의하여 c-plane 사파이어 상에서 성장되었으며, 전구체 농도가 0.01M에서 0.025M로 증가할 때의 형태적, 구조적, 광학적 성질의 변화에 대하여 주사전자현미경, X-선 회절분석기, 그리고 Photoluminescence(PL) 분석을 통하여 알아보았다. 전구체의 몰 분율이 증가함에 따라서 나노로드의 두께와 길이가 모두 증가하는 경향을 보였으며, 성장 방향은 모두 c-axis 방향임을 알 수 있었다. PL 측정에서의 380 nm파장의 강한 emission으로부터, 수열합성법에 의하여 성장된 ZnO 나노로드는 결함의 영향이 적고 양호하게 성장되어 있음을 확인할 수 있었다.

• 한국결정성장학회지
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• 제9권6호
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• pp.570-573
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• 1999

Ca nitrate와 인산을 혼합한 용액을 졸-겔법을 이용하여 Si(100) 기판 위에 스핀 코팅하여 열처리 함으로써 의치공 재료에 응용되는 하이드록시아파타이트 박막을 제조하였다. Si 기판 위에 아이드록시아파타이트막을 코팅하여 건조시킨 다음, $500^{\circ}C$에서 10분간 초벌구이 열처리를 하였다. X-선 회절 분석을 이용하여 $500^{\circ}C$에서 하이드록시아파타이트 상의 생성을 확인하였고, $500^{\circ}C$~$700^{\circ}C$ 및 $900^{\circ}C$에서 각각 tricalcium phosphate상의 생성을 확인하였다. FTIR(Fourier transform infrared spectroscopy)의 결과를 바탕으로 열처리 온도 증가에 따른 탄소량의 변화와 결정화도의 증가를 확인하려 한다.

• 전기학회논문지
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• 제67권10호
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• pp.1317-1321
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• 2018

PVDF as a semicrystal polymer, having a structure with C-F dipole moments, has been widely investigated because of its excellent chemical stability, mechanical strength, and ferroelectricity. In this study, ferroelectic ${\beta}$ type - PVDF layer was prepared by using an electrostatic spray deposition method and the effects of the addition of Ni-nitrate in precursor solution on the properties of PVDF layer were evaluated. Crystallinity and chemical structure of the PVDF layer were analyzed by a X-ray diffraction and Fourier Transform Infrared Spectrophotometer. Surface structure and fractured cross section of the layer were examined by a field emission-scanning electron microscope. LCR meter was used to obtain the dielectric properties of the layer. As the addition of an inorganic metal salt in PVDF sol, ${\beta}$ type - PVDF crystals were appeared in the hydrated metal salts doped-layer since the strong hydrogen bondings $(O-H{\cdots}F-C)_n$ due to high polarity of OH- were formed.

• 한국세라믹학회지
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• 제40권8호
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• pp.720-724
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• 2003

Aluminum nitride (AlN) powders were synthesized by using a mixture of an aluminum nitrate or sulfate salt and carbon (mole ratio of $Al^{3+}$ to carbon=L : 30). The AlN was obtained by calcining the mixture under a flow of nitrogen in the temperature range 1100-1$600^{\circ}C$ and then burning out the residual carbon. The process of conversion of the salt to AlN was monitored by XRD and $^{27}$ Al magic-angle spinning (MAS) NMR spectroscopy. The salt decomposed to ${\gamma}$-alumina and then converted to AlN without phase transition from ${\gamma}$-to-$\alpha$-alumina. $^{27}$ Al MAS NMR spectroscopy shows that the formation of AlN commenced at 110$0^{\circ}C$. AlN powders obtained from the sulfate salt were superior to those from the nitrate salt in terms of homogeneity and crystallinity. A very small amount of AlN whiskers was obtained by calcining a mixture of an aluminum sulfate salt and carbon at 115$0^{\circ}C$ for 40 h, and the growth of the whiskers is well explained by the particle-to-particle self-assembly mechanism.

• Progress in Superconductivity
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• 제7권1호
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• pp.52-57
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• 2005

[ $YBa_{2}Cu_{3}O_y$ ] superconducting films were prepared on $LaAlO_3$(100) single crystal substrate by spray pyrolysis method. The precursor solution was prepared by dissolving nitrate powders in de-ionized water. Both of ultrasonic and concentric nebulizers were used in order to generate fine droplets of precursor solution. C-axis oriented films were obtained at deposition temperature of $750\~850^{\circ}C$ and working pressure of 100 Torr and 500 Torr. In case of ultrasonic nebulizer, films showed rough and porous surface morphology due to formation of enormous droplets, while smooth and dense films were obtained for concentric nebulizer. A transport $J_c$ value of $0.43\;MA/cm^2$ at 77 K and self field was achieved on $LaAlO_3$(100) single crystal substrate.

• 한국세라믹학회지
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• 제35권5호
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• pp.451-457
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• 1998

$Li_2$$ZrO_3$ powder which is one of the candidates of breeding materials for the fusion reactor was syn-thesized by a precipitation-combustion process. Although precipitates from the reaction between zirconium nitrate and citric acid were existed in a precursor solution. $Li_2$$ZrO_3$ could easily be obtained by using the mixed fuel of urea and citric acid in stoichiometric composition. The phases of as-synthesized powder con-sisted of $Li_2$$ZrO_3$ and small amounts of $Li_6$$Zr_2O_3$ and $Li_2$$ZrO_3$ The latter phases disappeared after the cal-cination at $1100^{\circ}C$ for 2 h. The primary particle size and the specific surface area of as-synthesized powders were smaller than 20nm and 10-14 $M^2$/g, respectively. The primary particle size of the precipitation-combustion synthesized powders was affected by the size of precipitates present in a precursor solution.