• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.147-147
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• 2013

Multiferroic material $BiFeO_3$ (BFO) is a typical multiferroic material with a room-temperature magnetoelectric coupling in view of high magnetic- and ferroelectric-ordering temperatures (Neel temperature $T_N$ ~ 647 K and Curie temperature TC ~1,103 K). Rare-earth ion substitution at the Bi sites is very interesting, which induces suppressed volatility of the Bi ion and improved ferroelectric properties. At the same time, the Fe-site substitution with magnetic ions is also attracting, since the enhanced ferromagnetism was reported. In this study, BFO, $Bi_{0.9}Dy_{0.1}FeO_3$ (BDFO), $BiFe_{0.97}Co_{0.03}O_3$ (BFCO) and $Bi_{0.9}Dy_{0.1}Fe_{0.97}Co_{0.03}O_3 $ (BDFCO) compounds were prepared by conventional solid-state reaction and wet-mixing method. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ for 24 h. The samples were immediately put into an oven, which was heated up to 800oC and sintered in air for 1 h. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies). Dy and Co co-doping at the Bi and the Fe sites induce the enhancement of both magnetic and ferroelectric properties of $BiFeO_3$.

• 자원환경지질
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• 제28권4호
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• pp.351-367
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• 1995

보포트-맥켄지 분지의 리인디어 D-27 시추공 시료에 대한 원소 지화학 및 산소동위원소 연구가 수행되었다. $K_2O$, Rb, 희토류원소의 함량 증가, Mg, Ti, Sc, Zn, Zr 등의 팔면체 원소의 감소, Be, V 등의 사면체 원소의 증가는 깊이에 따라 일라이트층의 구성비가 증가하는 일라이트/스멕타이트의 속성경향과 대비된다. 스멕타이트층과 일라이트층의 구조식은 각각 $[Al_{1.57}Fe_{.19}Mg_{.31}Ti_{.07}][Si_{3.84}A_{1.16}]O_{10}(OH)_2$와 $[Al_{1.84}Mg_{.16}][Si_{3.33}Al_{.67}]O_{10}(OH)_2$로 추정된다. 일라이트/스멕타이트의 속성과 연관하여 희토류원소의 유동이 관찰되었다. 희토류원소, 특히 La와 Ce의 깊이에 따른 함량 증가는 높은 전하가를 갖는 사면체 원소 ($V^{5+}$)의 유입과 관련이 있다. $V^{5+}$에 의한 잉여 전하는 부분적으로 낫은 전하가를 갖는 $Be^{2+}$에 의하여 상쇄되며, 또한 $Be^{2+}$에 의하여 발생되는 지엽적인 전하 불균형은 층간 이온으로는 높은 전하가 (+3)를 갖는 희토류 원소에 의하여 해소된다. 일라이트/스멕타이트의 ${\delta}^{18}O$가 (SMOW)는 2.91~15.72‰의 범위를 보이며, 걸프연안 등의 일라이트/스멕타이트와는 달리 깊이에 따라 증가한다. 일라이트/스멕타이트의 ${\delta}^{18}O$가의 증가는 공극수의 ${\delta}^{18}O$ 증가도가 깊이에 따라 증가하는 온도로 인한 동위원소 분별작용정수 (${\Delta}_{I/S-water}$)의 감소도보다 크기 때문이다. 일라이트/스멕타이트와 평형인 공극수의 ${\delta}^{18}O$가의 계산결과는 공극수의 근원이 지표수임을 지시한다. 중간 깊이에서 낮은 ${\delta}^{18}O$가를 보이는 450m 두께의 구간은 공극수가 층상화되어 있음을 의미한다. 그러나 이 깊이 구간이 낮은 일라이트층 구성비와 낮은 $K_2O$ 함량을 보이는 구간과 일치하지 않는 것으로 볼때 동위원소 교환 반응과 광물학적, 지화학적 반응은 서로 독립적으로 일어나는 것으로 해석된다.

• 자원환경지질
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• 제48권3호
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• pp.255-260
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• 2015

지구상에는 2000종 이상의 광물이 존재하고 있으며 환경, 건축, 축산, 화학, 의약 등의 다양한 분야에서 활용되고 있다. 그 중 점토광물은 흡착과 방출을 통해 물리 화학적인 성질이 변할 수 있는 특징이 있다. 국내 비금속 광물자원의 매장량은 약 96억 톤으로 그 자원 효용이 높은데 반해 고부가가치화를 이루지 못하고 있는 실정이다. 또한 벤토나이트와 제올라이트를 이용한 제품들이 화장품과 생활용품, 포장재 등에 일부 사용되고 있지만 잠재적인 가치 측면에서 무한한 가능성을 지닌 식품산업에 활용된 사례는 사실상 전무하다. 광물자원에 대한 식품/약용으로의 섭취기록은 이미 오래 전부터 문헌상으로 존재하고 있으며, 국내 매장량이 높은 자원임을 감안할 때 식품 소재로서의 활용가치는 상당하리라 생각된다. 점토광물의 특허 동향 조사를 통해 미국, 유럽을 비롯한 세계 각국이 기업체를 중심으로 광물자원을 식품산업에 적용하기 위한 기술을 개발 중이며, 관련 산업이 성장시기에 있다는 것을 확인할 수 있었다. 따라서 본 논문에서는 국내외 광물자원 관련 식품산업분야 특허 동향과 광물자원의 식품산업분야 이용 및 규제 현황에 관한 정보를 제공하고, 이를 바탕으로 향후 광물자원을 식품분야에 어떻게 활용할 지에 대한 적용 방안을 제시하고자 한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.260-260
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• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.258-292
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• 1996

In the last year great interest appears to YBCO thin films preparation on different substrate materials. Preparation of epitaxial film is a very difficult problem. There are many requirements to substrate materials that must be fullfilled. Main problems are lattice mismatch (misfit) and similarity of structure. From paper [1] or follows that difference in interatomic distances and angles of substrate and film is mire important problem than similarity of structure. In this work we present interatomic distances and angle relations between substrate materials belonging to ABCO4 group (where A-Sr or Ca, B-rare earth element, C-Al or Ga) of different orientations and YBCO thin films. There are many materials used as substrates for HTsC thin films. ABCO4 group of compounds is characterized by small dielectric constants (it is necessary for microwave applications of HTsC films), absence of twins and small misfit [2]. There most interesting compounds CaNdAlO4, SrLaAlO4 and SrLaGaO4 were investigated. All these compounds are of pseudo-perovskite structure with space group 14/mmm. This structure is very similar to structure of YBCO. SLG substrate has the lowest misfit (0.3%) and dielectric constant. For preparation of then films of substrates of this group of compound plane of <100> orientation are mainly used. Good quality films of <001> orientations are obtained [3]. In this case not only a-a misfit play role, but c-3b misfit is very important too. Sometimes, for preparation of thin films substrates of <001> and <110> orientations were manufactured [3]. Different misfits for different YBCO faces have been analyzed. It has been found that the mismatching factor for (100) face is very similar to that for (001) face so there is possibility of preparation of thin films on both orientations. SrLaAlO4(SLA) and SrLaGaO4(SLG) crystals of general formula ABCO4 have been grown by the Czochralski method. The quality of SLA and SLG crystals strongly depends on axial gradient of temperature and growth and rotation rates. High quality crystals were obtained at axial gradient of temperature near crystal-melt interface lower than 50℃/cm, growth rate 1-3 mm/h and the rotation rate changing from 10-20pm[4]. Strong anisotropy in morphology of SLA and SLG single crystals grown by the Czochralski method is clearly visible. On the basics of our considerations for ABCO4 type of the tetragonal crystals there can appear {001}, {101}, and {110} faces for ionic type model [5]. Morphology of these crystals depend on ionic-covalent character of bonding and crystal growth parameters. Point defects are observed in crystals and they are reflected in color changes (colorless, yellow, green). Point defects are detected in directions perpendicular to oxide planes and are connected with instability of oxygen position in lattice. To investigate facets formations crystals were doped with Cr3+, Er3+, Pr3+, Ba2+. Chromium greater size ion which is substituted for Al3+ clearly induces faceting. There appear easy {110} faces and SLA crystals crack even then the amount of Cr is below 0.3at.% SLG single crystals are not so sensitive to the content of chromium ions. It was also found that if {110} face appears at the beginning of growth process the crystal changes its color on the plane {110} but it happens only on the shoulder part. The projection of {110} face has a great amount of oxygen positions which can be easy defected. Pure and doped SLA and SLG crystals measured by EPR in the<110> direction show more intensive lines than in other directions which allows to suggest that the amount of oxygen defects on the {110} plane is higher. In order to find the origin of colors and their relation with the crystal stability, a set of SLA and SLG crystals were investigated using optical spectroscopy. The colored samples exhibit an absorption band stretching from the UV absorption edge of the crystal, from about 240 nm to about 550 m. In the case of colorless sample, the absorption spectrum consists of a relatively weak band in the UV region. The spectral position and intensities of absorption bands of SLA are typical for imperfection similar to color centers which may be created in most of oxide crystals by UV and X-radiation. It is pointed out that crystal growth process of polycomponent oxide crystals by Czochralski method depends on the preparation of melt and its stoichiometry, orientation of seed, gradient of temperature at crystal-melt interface, parameters of growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth. Growth parameters have an influence on the morphology of crystal-melt interface, type and concentration of defects.