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Effect of process gas on deposition efficiency of zirconia film in granule spray in vacuum
Ochirkhuyag Tungalagtamir,Yoon-Soo Park,Jaewon Lee,Scooter D. Johnson,Dong-Soo Park,Chan Park 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.5
Monoclinic zirconia films were deposited by spraying monoclinic zirconia granules on glass substrates in a low vacuumenvironment. In order to spray the granules through a nozzle, air and He were used to carry and accelerate the granules. Flowrates of air and He were varied in order to study their effect on granule velocity and deposition efficiency. For both air andHe, granule velocity increased with their flow rate. For the same gas flow rate, granule velocity was much higher when Hewas used than when air was used. Variation of deposition efficiency according to the gas and gas flow rate was similar to thatof granule velocity. Highest deposition efficiency was 1.87% which may be the highest deposition efficiency of ceramic filmsby room temperature spray of ceramic particles or granules to date. The results support that granule velocity is closely relatedto deposition efficiency. The deposited films were quite dense and retained the crystalline phase of the granules.
에어로졸 증착법에 의해 제조된 PZN-PZT 후막의 전기적특성
Ochirkhuyag Tungalaltamir,장주희,박윤수,박동수,박찬 한국결정성장학회 2020 韓國結晶成長學會誌 Vol.30 No.5
Lead zinc niobate (PZN)-added lead zirconate titanate (PZT) thick films with thickness of 5~10 μm were fabricated on silicon and sapphire substrates using aerosol deposition method. The contents of PZN were varied from 0 %, 20 % and to 40 %. The PZN-added PZT film showed poorer electrical properties than pure PZT film when the films were coated on silicon substrate and annealed at 700°C. On the other hand, the PZN-added PZT film showed higher remanent polarization and dielectric constant values than pure PZT film when the films were coated on sapphire and annealed at 900°C. The ferroelectric and dielectric characteristics of 20 % PZN-added PZT films annealed at 900°C were compared with the result values obtained from bulk ceramic specimen with same composition sintered at 1200°C. As annealing temperature increased, dielectric constant increased. These came from enhanced crystallization and grain growth by post heat treatment. 에어로졸 증착법에 의해서 상온에서 5~10 μm 두께의 PZN-PZT(0 %, 20 %, 40 %) 복합체의 막을 실리콘/사파이어 기판 위에서 제조하였다. PZN의 농도는 0 %, 20 % 및 40 %까지 첨가하였다. 실리콘기판 및 사파이어 기판 위에서 증착된 막은 전기로에서 700°C 및 900°C에서 각각 어닐링처리 하였으며 900°C에서 어닐링한 경우의 잔류분극 및 유전 상수 등의 전기적 특성이 700°C에서의 특성보다 우수하였다. 특히 900°C에서 어닐링한 2PZN-8PZT 막의 경우 1200°C에서 소결한같은 조성의 벌크재에서 얻은 값과 상호 비교하였다. 열처리 온도가 높아짐에 따라 유전상수가 증가하는 경향을 보이는데이는 후열처리에 따른 막의 결정성의 향상과 입자 성장으로 기인한다.
Giant Magnetic Anisotropy in Metastable FePt Alloy
T. Ochirkhuyag,S. C. Hong,D. Tuvshin,E. Uranbaigal,D. Odkhuu 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2
As information storage and high-speed permanent magnet motor technologies have evolved, high-performance permanent magnetic materials with large saturation magnetization and magnetic anisotropy (MA) become indispensable. In this presentation, we report results of first-principles calculations on structural and intrinsic magnetic properties of L10-ordered FePt alloy along the so-called Bain path. Our total energy calculations reveal that the body centered tetragonal (bct) structure of FePt with c/a=0.85 is identified as a metastable phase, which can be epitaxially grown on an appropriate substrate. More remarkably, both saturation magnetization and uniaxial MA of this bct metastable phase are significantly larger compared with those of the ground state L10-FePt and other known magnetic materials. Single-particle energy spectrum analyses indicate that while the Pt 5d orbital states determine the MA-driven permanent magnetic properties in L10-FePt alloy, the large enhancement of MA in the metastable structure mainly originates from the Fe 3d orbital states. We will also discuss our more recent findings on possibilities of further improving the performance of the metastable permanent magnet FePt with a series of 3d and 4d transition metal dopant elements.
Tumentsereg Ochirkhuyag,Soon Cheol Hong,Dorj Odkhuu 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
Herein we propose a possible solution to realize an otherwise unstable ThMn<sub>12</sub>-type SmFe<sub>12</sub> permanent magnet through systematic full-potential density functional theory and Monte Carlo simulations on ternary Sm−Fe−M compounds (M is a 3d or 3p metal substitute atom). Among the 11 metal elements (Ti−Ga and Al), only the simple metal Al, rather than the traditional transition metal substitute atoms, is predicted to be optimal; not only stabilizes the ThMn<sub>12</sub> structure with improved single-domain grain size but also promotes superior intrinsic magnetic properties at room temperature, including the uniaxial magneto crystalline anisotropy (MA) up to 6.7 MJ·m<sup>-3</sup>, anisotropy field up to 16.4 T, and hardness parameter up to 3, to the state-of-the-art permanent magnet Nd<sub>2</sub>Fe<sub>14</sub>B. Numerical results of MA and MA-driven hard magnetic properties are described by the strong spin-orbit coupling and orbital angular momentum of the Sm 4 f-electron orbitals. The other simple metal Ga, which is isoelectronic to Al, makes the present argument rather general, stabilizing the ThMn<sub>12</sub> phase while still preserving MA uniaxial.