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Mossbauer Study of nano-sized (Li_{0.5x}Fe_{0.5x}Zn_{1-x})Fe_2O_4$ particles

  • J. C. Sur;Kim, T. S.;T. Y. Ha;Lee, J. K.;S. H. Gee;Y. K. Hong;Park, M. H.;D. W. Erickson;P. J. Lamb
    • Proceedings of the Korean Magnestics Society Conference
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    • 2002.12a
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    • pp.92-93
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    • 2002
  • The substituted lithium ferrites combine useful ferromagnetic properties with high Curie temperature ranging from 55$0^{\circ}C$ to 85$0^{\circ}C$, [1] high saturation magnetization, [2] and low microwave dielectric loss.[3] Saturation magnetization of (Z $n_{1-x}$ F $e_{x}$)A[L $i_{0.5x}$F $e_{ 2-0.5x}$]$_{B}$ $O_4$ increased with zinc concentration, followed by a decrease at x = 0.7.[4] This is attributed to a dilution of the A-site with zinc which initially causes an increase in saturation magnetization due to the dominance of the B-site. (omitted)d))d)d))

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A Study OH Mossbauer Spectra Of the $Li_{0.5}Fe_{2.5-x}Al_xO_4$ Ferrite System (Li_{0.5}Fe_{2.5-x}Al_xO_4 페라이트계의 Mossbauer 스펙트럼 연구)

  • 백승도
    • Journal of the Korean Magnetics Society
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    • v.11 no.2
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    • pp.58-62
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    • 2001
  • The L $i_{0.5}$F $e_{2.5-x}$A $l_{x}$ $O_4$ systems (x=0, 0.3, 0.6, 0.9, 1.2, 1.5) were investigated by X-ray diffraction and Mossbauer spectroscopy. The structure of all the samples is cubic spinel type and lattice constant decrease with increasing Al content x. The Moissbauer spectra reveal two sextet for 0$\leq$x$\leq$0.6, two sextet and a doublet for 0.9$\leq$x$\leq$1.2, and a doublet for x=1.5. The cation distribution of the samples is (L $i_{1-a}$$^{+}$F $e_{a}$ $^{3+}$)$^{A}$[L $i_{a-0.5}$$^{+}$A $l_{2.5-a-x}$$^{+}$F $e_{2.5-a-x}$$^{3+}$]$^{B}$ $O_4$$^{2-}$ and substituted $Al^{3+}$ ions decrease the covalency of F $e^{3+}$- $O^{2-}$ bond in B-sites and A-B super-exchange interactions.tions.s.tions.ons.s.

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Enhancement and optimization of gamma radiation shielding by doped nano HgO into nanoscale bentonite

  • Allam, Elhassan A.;El-Sharkawy, Rehab M.;El-Taher, Atef;Shaaban, E.R.;RedaElsaman, RedaElsaman;Massoud, E. El Sayed;Mahmoud, Mohamed E.
    • Nuclear Engineering and Technology
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    • v.54 no.6
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    • pp.2253-2261
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    • 2022
  • In this study, nano-scaled shielding materials were assembled and fabricated by doping different weight percentages of Nano-mercuric oxide (N-HgO) into Nano-Bentonite (N-Bent) based on using (100-x% N-Bent + x% N-HgO, x = 10, 20, 30, and 40 wt %). The fabricated N-HgO/N-Bent nanocomposites were characterized by FT-IR, XRD, and SEM and evaluated to evaluate their shielding properties toward gamma radiation by using four different γ-ray energies form three point sources; 356 keV from 133Ba, 662 keV from 137Cs as well as 1173, and 1332 keV from 60Co. The γ-rays mass attenuation coefficients were plotted as a function of the doped N-HgO concentrations into N-HgO/N-Bent nanocomposites. The computed values of mass attenuation coefficients (µm), effective atomic number (Zeff) and electron density (Nel) by the as-prepared samples were found to increase, while the half value layer (HVL) and mean free path (MFP) were identified to decrease upon increasing the N-HgO contents. It was concluded also that the increase in N-HgO concentration led to a direct increase in the mass attenuation coefficient from 0.10 to 0.17 cm2/g at 356 keV and from 0.08 to 0.09 cm2/g at 662 keV. However, a slight increase was observed in the identified mass attenuation coefficients at (1172 and 1332 keV).

Analysis of Grain Boundary Phenomena in ZnO Varistor Using Dielectric Functions (유전함수를 이용한 ZnO 바리스터의 입계 특성 분석)

  • Hong, Youn-Woo;Shin, Hyo-Soon;Yeo, Dong-Hun;Kim, Jong-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.178-178
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    • 2008
  • ZnO 바리스터는 인가되는 전압에 따라 저항이 변하는 전압 의존형 저항체이며 각종 전기 전자 정보통신용 제품에 정전기(ESD) 대책용 소자로 폭 넓게 사용되는 전자 세라믹스 부품이다. 특별히 Bi-based ZnO 바리스터는 다양한 상(phase)으로 구성되어 있으며 그 입계의 전기적 특성은 소량 첨가되는 dopant의 종류에 따라 다양하게 변하는 것으로 알려져 있다. 본 연구에서는 Bi-based ZnO 바리스터 (ZnO-$Bi_2O_3$, ZnO-$Bi_2O_3-Mn_3O_4$)에서 각종 유전함수$(Z^*,M^*,\varepsilon^*,Y^*,tan{\delta})$를 이용하여 입계의 주파수-온도에 대한 특성을 살펴 보았다. 일반적인 ZnO 바리스터 제조법으로 시편을 제작하여 78K~800K 온도 범위에서 각종 유전함수를 이용하여 복소 평면도(complex plane plot)와 주파수 응답도(frequency explicit plot)의 방법으로 defect level과 입계 특성(활성화 에너지, 정전용량, 저항, 입계 안정성 등)에 대하여 고찰하였다. ZnO-$Bi_2O_3$(ZB)계와 ZnO-$Bi_2O_3-Mn_3O_4$(ZBM)계 모두 상온 이하의 온도에서 $Zn_i$$V_o$의 결함이 나타났으며, 이들의 결함 준위는 각 유전함수에 따라 다소 차이가 났다. 입계 특성으로 ZB계는 이상구간(560~660K)을 전후로 1.15 eV $\rightarrow$ 1.49 eV의 활성화 에너지의 변화가 나타났지만, ZBM계는 이러한 현상이 나타나지 않았다. 또한 입계 전위 장벽의 온도 안정성에 대해서는 Cole-Cole model을 적용하여 분포 파라미터 (distribution parameter; $\alpha$)를 구하여 고찰하였다. ZB계의 입계 안정성은 온도에 따라 불안정해 졌지만, ZBM계는 안정하였다.

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The Hyperfine Interaction for the FeIn2S4 by Mössbauer Spectroscopy (뫼스바우어 효과를 통한 FeIn2S4에서의 Fe2+ 초미세 상호 작용 연구)

  • Son, Bae-Soon;Kim, Sam-Jin;Kim, Chul-Sung
    • Journal of the Korean Magnetics Society
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    • v.17 no.1
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    • pp.30-33
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    • 2007
  • The $FeIn_2S_4$ exhibits an inverse spinel which Fe ions are occupied to the octahedral(B) site, while In ions are occupied to both the tetrahedral(A) and the octahedral(B) site. The $N\'{e}el$ temperature($T_N$) is determined to be 13 K. The effective moment of $FeIn_2S_4$ found to be $5.094{\mu}_B$ from the fit of Curie-Weiss inverse susceptibility for the temperature range over $T_N$, implying angular momentum contribution. The angular momentum contribution is shown in $M\"{o}ssbauer$ spectra for the antiferromagnetic ordering region($T{\leq}\;13K$), too. A weak $Fe^{2+}(B)-S^2-Fe^{2+}(B)$ interaction is responsible for a low $N\'{e}el$ temperature($T_N$) in $FeIn_2S_4$ system. The temperature dependence of electric quadrupole interaction is explained by z-axial crystalline field energy.

Die Organisation von Mikrostrukturen der zweisprachigen $W\"{o}rterb\"{u}cher$ Deutsch/Koreanisch (독-한 두말사전의 미시구조 조직)

  • Kim Kyong
    • Koreanishche Zeitschrift fur Deutsche Sprachwissenschaft
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    • v.5
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    • pp.183-202
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    • 2002
  • Die vorliegende Arbeit verfolgt zwei Ziele: zum einen sollen die Entwicklungen in der modernen zweisprachigen Lexikographie mit Ausgangssprache Deutsch skizzenhaft vorgestellt und einige Forschungsdefizite benannt werden, zum anderen sollen die Ergebnisse und Methoden der neueren Lexikographie anhand von Beispielartikeln der drei $einschl\"{a}gigen$ deutsch-koreanischen $Gro{\ss}w\"{o}rterblicher$ kontrastiert und diskutiert werden. Zuerst wird eine Typologie der zweisprachigen $W\"{o}rterb\"{u}cher$ erstellt, derzufolge es jeweils 2 aktive und 2 passive Worterblicher pro Sprachenpaar gibt. Das Aktiv-Passiv­Prinzip gilt als ein grundlegender Ausgangspunkt $f\"{u}r$ die zweisprachige Lexikographie. Eine Erweiterung der Unterscheidungskriterien scheint nicht $zweckm\"{a}{\ss}ig$ und angesichts praktischer Schwierigkeiten auch kaum realisierbar. $Pl\"{a}diert\;wird\;f\"{u}r\;eine\;st\"{a}rkere\;Ber\"{u}cksichtigung$ der Benutzungssituationen, zu denen z.B. der Grad der Sprachbeherr­schung der jeweiligen Benutzergruppe, die $m\"{o}glichen\;Benutzungsanl\"{a}sse$, der Kenntnisstand $bez\"{u}glich$ der Benutzerhinweise sowie die technische Geschicklichkeit bei der $W\"{o}rterbuch-benutzung\;etc.\;zu\;z\"{a}hlen$ sind. In makrostruktueller Hinsicht werden die Selektion und die Anordnung der Lemmata diskutiert. Bei der Lemmaauswahl $w\"{a}re\;es\;w\"{u}nschenswert$, auf der Grundlage eines Lemmavergleiches der verschiedensten Quellenworterbucher ein datenbasiertes Korpus zu erstellen. Dazu $k\"{o}nnten$ folgende Materialien ausgewertet werden: (1) einsprachige allgemeine (ad spezielle) $W\"{o}rterb\"{u}cher$ (z.B. Deutsch/Koreanisch), (2) zweisprachige allgemeine (od spezielle) Worterblicher (z.B. Deutsch-Koreanisch, Deutsch-Englisch) etc. Die $blo{\ss}e\;\"{U}bersetzung$ lediglich eines einzigen $Quellenw\"{o}rterbuches\;k\"{o}nnte$ dagegen zu $unerw\"{u}nschten\;Einseitigkeiten\;f\"{u}hren$. Was die Anordnung der Lemmata in zweisprachigen $W\"{o}rterb\"{u}chern$ betrifft, $k\"{o}nnen$ dieselben drei makrostrukturellen Typen unterschieden werden, wie in einsprachigen $W\"{o}rterb\"{u}chern$: (1) glattalphabetisch, (2) nischenalphabetisch, (3) nestalphabetisch. Unter den zu untersuchenden $W\"{o}rterb\"{u}chern$ weisen das EDK und das HDK die nischenalpha­betische Makrostruktur auf, das MDK ist dagegen nestalphabetisch angeordnet. Je nachdem, wie die Polysemiestruktur und die Mehr-Wort-Einheit kombinieren, werden die drei Arten der Mikrostruktur unterschieden: (1) die integrierte Mikrostruktur, (2) die nichtintegrierte Mikrostruktur, (3) die partiell integrierte Mikrostruktur. $W\"{a}hrend$ das EDK und das HDKeine integrierte Mikrostruktur besitzen, weist das HDK eine partiell integrierte Mikrostruktur auf. Die Artikelgestaltung durch die nichtintegrierte Mikrostruktur, die $h\"{a}ufig$ in der zweisprachigen Lexikographie angewandt wird und entsprechende Vorteile besitzt, sallte $k\"{u}nftig\;als\;Gestaltungsm\"{o}glichkeit\;st\"{a}rker$in Betracht gezogen werden. In Bezug auf die Organisation der Mikrostruktur werden vier Bauteile, das sind Lemma-, $\"{A}quivalent-$, Diskriminator- und Beispielangaben untersucht. Die $\"{U}bersetzungs\"{a}quivalente$ werden je nach dem lexikalisch-semantischen Abdeckungsgrad mit dem Lemma in drei Typen eingeteilt: (1) $Voll\"{a}quivalent,\;(2)\;Teil\"{a}quivalent,\;(3)\;Null\"{a}quivalent$. In der Mehrheit kommen die Teil- oder $Null\"{a}quivalente$ vor, weil die ausgangssprachlichen Lemmata und die zielsprachlichen $\"{A}quivalente$ in sich Polysemiestruktur aufweisen. $Informationsm\"{a}ngel$ auszugleichen ist die Funktion des Diskriminators, in dem Glosse, Markierungen und metasprachliche $Erl\"{a}uterungen$ zusammenwirken. $Verbesserungsw\"{u}rdig\;sind\;die\;g\"{a}ngigen$ deutsch-koreanischen $W\"{o}rterb\"{u}cher$ var allem im Hinblick auf die stilistischen Markierungen; die Inkongruenz des Stils zwischen den beiden verschiedenen Sprachen wird bislang zu wenig $ber\"{u}cksichtigt$ und sagar in ein und demselben $W\"{o}rterbuch$ nicht konsequent dargestellt. Trotz der relativen $Geringsch\"{a}tzung$ von Beispielangaben in der $europ\"{a}ischen$ zweisprachigen passiven Lexikographie sallte diesen in deutsch-koreanischen $W\"{o}rterb\"{u}chern$ mehr Aufmerksamkeit gewidrnet werden. Sie sind dem koreanischen Benutzer eine wichtige Hilfe, indem sie die $\"{A}quivalentenangaben\;implizite\;erg\"{a}nzen$ und Informationen $\"{u}ber$ die syntaktisch-semantische und pragmatische Kontextrestriktion bieten. $Dar\"{u}berhinaus$ stellen sie selbst interessante kulturelle, geistige und landeskundliche etc. Informationen dar. Was den Artikelaufbau betrifft, wird das Van Dale-Modell diskutiert, d.h. das kategoriell-semantisch-alphabetische Prinzip, das trotz mancher Kritikpunkte viele interessante Anregungen $f\"{u}r$ die zweisprachige Lexikographie Deutsch-Koreanisch bietet, wo z.B. noch nicht die $Pr\"{a}positionen$ in der Beispielangabe durch typographische Hervorhebung $pr\"{a}sentiert$ worden sind. Aus $Platzgr\"{u}nden$ sind hier nur wenige Beispielartikel mit substantivischen Lemmata $angef\"{u}hrt$ und analysiert worden. Um die $h\"{o}here$ Generalisierbarkeit zu erreichen, brauchen die Untersuchungs- materialien mindestens einen bestimmten Umfang. Derartige empirische Forschungen $k\"{o}nnen$ als Impulse dazu beitragen, $k\"{u}nftige\;W\"{o}rterb\"{u}cher$ im Sinne einer $Ber\"{u}cksichtigung$ neuerer lexikographischer Erkenntnisse verbessern zu helfen.

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AN ELECTRONMICROSCOPIC STUDY ON THE HEALING PROCESS OF THE REMAINING PULPAL TISSUES AFTER PULPOTOMY BY Nd-YAG LASER (Nd-YAG레이저에 의한 치수 절단후 잔존 치수 조직의 치유과정에 관한 전자현미경적 연구)

  • Park, Dong-Sung;Lim, Sung-Sam
    • Restorative Dentistry and Endodontics
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    • v.20 no.2
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    • pp.399-422
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    • 1995
  • The purpose of this study was to investigate a fragment of possibility of pulpotomy with the Nd-YAG laser by the observation of pulpal healing process and the fine structural changes of the fibroblasts of the remaining pulpal tissues. Class V cavities on !55 teeth from 4 adult dogs were prepared and the pulp chambers were opened with a sterilized round bur. In the control group(19 teeth), the exposed coronal pulps were excised by a sharp excarvator. After bleeding was controlled with the sterilized cotton pellets, calcium hydroxide powder was applied on the remaining pulpal tissues and the cavities were sealed with Z.O.E. In the experimental group 1 : the pulpotomy with laser-calcium hydroxide powder application group(l9 teeth), the exposed coronal pulps were excised by Nd-YAG laser(10 watts power, 2 psi water, 20 psi air) for 2 or 3 seconds and calcium hydroxide powder was applied on the remaining pulpal tissues and the cavities were sealed with Z.O.E. In the experimental group 2 : the pulpotomy with laser-no calcium hydroxide powder application group(17 teeth), after amputating the coronal pulps with Nd-YAG laser as the experimental group 1, the remaining pulpal tissues were covered with stenilized aluminum foil and the cavities were filled with Z.O.E. The animals were sacrificed at the intervals of 1, 2, 3 and 4 weeks. All the teeth were rouutinely processed and the remaining pulpal tissues were observed by the light microscope and electron microscope. The results were as follows : 1. In light microscopic findings, there was no significant difference of the inflammatory response in the remaining pulpal tissues between the control group and the experimental groups. In both of the experimental group 1 : pulpotomy with laser-calcium hydroxide powder application group and the control group, the dentin bridges were observed after 2 weeks and the structure of the dentin bridge was almost same. In the experimental group 2 : pulpotomy with laser-no calcium hydroxide powder application group, the fibrous layers instead of dentin bridge were observed on the superficial portion of the remaining pulpal tissues after 2 weeks and they were consisted with densely crowded active fibroblasts. 2. In the electronmicroscopic findings, the active fibroblasts in the experimental groups were more frequently observed than in the control group at 1 week. But active fibroblasts were found with same frequency after 2 weeks in all of the control group and the experimental groups. 3. General distortions of the cell such as loss of the cell membrane, vaculoization of the cell etc. were observed at the suberficial layer of the remaining pulpal tissues and the carbonization was found in the dentinal wall in 1 week of the experimental groups. 4. In the experimental group 2 : pulpotomy with laser-no calcium hydroxide powder application group, the activity and the density of the fibroblasts in the fibrous layer were more than those in the deep portion of the remaining pulpal tissues after 2 weeks. 5. In the control group, bacteria such as cocci and bacilli were observed frequently, but in the experimntal groups, they could not be observed.

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Comparison of Luminescence Properties of Electrochemical Luminescence Cells for Various Electrode Materials and Structures

  • Pooyodying, Pattarapon;Ok, Jung-Woo;Sung, Youl-Moon
    • Journal of Electrical Engineering and Technology
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    • v.12 no.4
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    • pp.1605-1610
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    • 2017
  • The electrochemical luminescence (ECL) device was investigated, which has similar structure to the dye-sensitized solar cell. The structure of the ECL cell in this experiment reliably induces a large amount of the oxidation around electrodes. The band gap of the ECL electrode is of 3.0 - 3.2 eV. Titanium dioxide ($TiO_2$) nanoparticle has following properties: a band gap of 3.4 eV, a low-priced material, and 002 preferred orientation (Z-axis). Zinc Oxide (ZnO) nanorod is easy to grow in a vertical direction. In this paper, in order to determine material suitable for the ECL device, the properties of various materials for electrodes of ECL devices such as ZnO nanorod (ZnO-NR) and $TiO_2$ nanoparticle ($TiO_2-NP$) were compared. The threshold voltage of the light emission of the ZnO-NR was 2.0 V which is lower than 2.5 V of $TiO_2-NP$. In the other hand, the luminance of $TiO_2-NP$ was $44.66cd/m^2$ and was higher than that of $34cd/m^2$ of ZnO-NR at the same applied voltage of 4 V. Based on the experimental results, we could conclude that $TiO_2-NP$ is a more suitable electrode material in ECL device than the ZnO-NR.

Electrical Properties of PZT Thin Films Deposited on the Ru/$RuO_2$ Metal/Oxide Hybrid Electrodes (Ru/$RuO_2$ 금속/산화물 이중전극 위에 증착한 PZT 박막의 전기적 특성)

  • Jeong, Kyu-Won;Park, Young;Song, Joon-Tae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.4
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    • pp.281-288
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    • 2001
  • PZT thin films (3500$\AA$) have been prepard on the Ru/Ru $O_2$ and Ru $O_2$ bottom electrodes with a RF magnetron sputtering system using P $b_{1.05}$(Z $r_{0.52}$, $Ti_{0.48}$) $O_3$ ceramic target. Ru/Ru $O_2$ bottom electrode was fabricated by in-situ processing controlled the $O_2$ partial pressure. The PZT thin films deposited on the Ru/Ru $O_2$ bottom electrode were preferred oriented (101) plane. The PZT thin films deposited on the Ru/Ru $O_2$ bottom electrodes showed better electrical properties than those with Ru $O_2$ bottom electrodes because Ru $O_2$ prevented oxygen vacancies and impurities from existing withing the interface and substrate.e.

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Ferroelectric properties of the $Ba(La_{1/2}Nb_{1/2})O_3-Pb(Zr_yTi_{1-y})O_3$ceramics with $PbZrO_3$ contents (투광성 $Ba(La_{1/2}Nb_{1/2})O_3-Pb(Zr_yTi_{1-y})O_3$ 세라믹의 $PbZrO_3$조성에 따른 강유전 특성)

  • 류기원;이성갑;배선기;이영희
    • Electrical & Electronic Materials
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    • v.6 no.3
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    • pp.241-247
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    • 1993
  • 본 연구에서는 투광성 0.085Ba(L $a_{1}$2/N $b_{1}$2/) $O_{3}$- 0.915Pb(Z $r_{y}$ $Ti_{1-y}$) $O_{3}$(0.45.leq.y.leq.0.70)세라믹을 2단 소성법으로 제작한 후, PbZr $O_{3}$조성 및 온도에 따른 구조적, 강유전적특성을 측정하였다. XRD측정 결과, PbZr $O_{3}$조성이 감소할수록 결자상수 및 단위격자 체적은 감소하였으며 시편의 결정구조는 입방정계에서 능면체정계, 정방정계로 변화되었다. 8.5/60/40시편의 경우 포화분극, 잔류분극 및 항전계가 각각 33.28[.mu.C/$cm^{2}$], 4.15[kV/cm]로 전형적인 메모리 특성을 나타내었으며 PbZr $O_{3}$조성이 증가함에 따라 강유전 이력곡선은 slim loop특성을 나타내었다. 잔류분극은 온도가 증가함에 따라 감소하였으며 특히 PE-FE상경계 부근에 위치한 조성의 경우, 상전이 온도 이하의 온도에서 급격히 감소하는 경향을 나타내었다.다.

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