• Title, Summary, Keyword: $LaAlO_3$

Search Result 264, Processing Time 0.038 seconds

Toughening of $Al_2$O$_3$/LaAl$_{11}$O$_{18}$ Composites (Al$_2$O$_3$/LaAl$_{11}$O$_{18}$ 복합재료의 인성증진)

  • 장병국;우상국
    • Journal of the Korean Ceramic Society
    • /
    • v.35 no.12
    • /
    • pp.1266-1273
    • /
    • 1998
  • Al2O3/(5~20vol%)LaAl11O18 composites in which the second phase was dispersed with a elongated grain shape were fabricated using Al2O3 and La2O3 composition by hot-pressing. In order investigate the in-fluence of LaAl11O18 on the toughening of LaAl11O18 on the toughening of Al2O3 matrix composites AE(acoustic emission) analysis was con-ducted together with an evaluation of fracture toughness using of SEPB technique. The degree of AE events occurred in composites were more than those in monolithic alumina. The occurrences of AE event increased with increasing the amount of LaAl11O18 phase in the Al2O3/LaAl11O18 composite is two times higher compared to monolithic alu-mina. The main toughening mechanism was attributed to the bridging of LaAl11O18 grains at tip of pro-pagating crack.

  • PDF

Comparative studies of the mechanochemically treatment of $La_{2}O_{3}-Al(OH)_{3}$ (메카노케미컬 공정에 의한 $La_{2}O_{3}-Al_{2}O_{3}$$La_{2}O_{3}-Al(OH)_{3}$의 비교연구)

  • 조정호;최상수;김강언;정수태
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.701-704
    • /
    • 2001
  • The dielectric and sintering properties of LaAlO$_3$ceramics synthesised with La$_2$O$_3$-Al$_2$O$_3$(LAO) and La$_2$O$_3$-Al(OH)$_3$(LAH) were investigated. In case of LAH samples, a single phase of LaAlO$_3$powders was formed at 100$0^{\circ}C$, density of the ceramics sintered at 140$0^{\circ}C$ was 6.41g/㎤, and the dielectric constant and loss were 22.4 and 0.003, respectively. In case of LAO samples, a single phase of LaAlO$_3$powders was formed at 130$0^{\circ}C$, density of the ceramics sintered at 150$0^{\circ}C$ was 6.35g/㎤, and the dielectric constant and loss were 22.16 and 0.009, respectively.

  • PDF

Microwave Dielectric properties of $(1-x)La_{2/3}TiO_3-xLaAlO_3$System ($(1-x)La_{2/3}TiO_3-xLaAlO_3$계의 마이크로파 유전 특성)

  • 이경태;박현수;문종하
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.4
    • /
    • pp.368-372
    • /
    • 1997
  • The microwave dielectric properties of (1-x)La2/3TiO3-xLaAlO3 system in which LaAlO3 having $\varepsilon$r$\geq$90 and positive $\tau$f was investigated. The crystal system of (1-x)La2/3TiO3-xLaAlO3 was pseudo-cubic in the range of 0.1$\leq$x$\leq$0.07. Its lattice constant increased with increasing x in spite that the amount of LaAlO3 containing of smaller Al(0.57 $\AA$) ion than Ti(0.64 $\AA$) increased. As the amount of LaAlO3 increased from x=0.1 to 0.9, the relative dielectric constant ($\varepsilon$r) decreased from 50 to 23 and the temperature coefficient of resonant frequency($\tau$f) decreased from +84 to -50. On the other hand, the value of Q.f0 reached a maximum (148,000 at 7 GHz) at x=0.7, where a rapid increase in the peak intensity of XRD occured, and further increased after prolonged sintering. The microwave dielectric properties of $\varepsilon$r=37, Q.f0=47,000 (at 7 GHz), and $\tau$f=-2 ppm/$^{\circ}C$ were obtained near 0.6La2/3TiO3-0.4LaAlO3 (x=0.4) composition.

  • PDF

Sintering and Dielectric Characteristics of LaAlO3 Ceramics by Mechanochemical Treatment from La2O3-A12O3 and La2O3-Al(OH)3 (La2O3-Al2O3와 La2O3-Al(OH)3를 메카노케미칼로 처리한 LaAlO3세라믹스의 소결 및 유전특성)

  • 최상수;조정호;김강언;정수태;조상희
    • Journal of the Korean Ceramic Society
    • /
    • v.39 no.1
    • /
    • pp.68-73
    • /
    • 2002
  • The dielectric properties and synthesis of $LaAlO_3$ ceramics from mixtures of $La_2O_3-Al_2O_3$ (LAO) and $La_2O_3-Al(OH)_3$(LAH) via grinding process were investigated. The single phase $LaA1O_3$of LAO and LAH powders were formed at $1300^{\circ}C$ and $1000^{\circ}C$, respectively. A non-reacted $La_2O_3$ existing in calcined powder was changed to La(OH)$_3$by moisture in the air, and their samples were worse than those of the samples made from a $LaA1O_3$single phase powder. The densities of LAO samples sintered at 150$0^{\circ}C$ for 4 h and LAH samples sintered at $1400^{\circ}C$ for 4 h were 97.3% and 98.3% of theory density, respectively. Grains of LAH sample showed uniformity and their sizes were 0.75 ${\mu}{\textrm}{m}$, and LAO samples showed non-uniformity and their sizes were 4-5 ${\mu}{\textrm}{m}$. Dielectric constant of LAO and LAH samples were the same value (≒22), however dielectric loss of LAH sample (0.0003) were lower than that of LAO sample(0.001)due to grain size.

Effect of La in Partial Oxidation of Methane to Hydrogen over M(1)-Ni(5)/AlCeO3 (M = La, Ce, Y) Catalysts (M(1)-Ni(5)/AlCeO3 (M = La, Ce, Y) 촉매상에서 수소 제조를 위한 메탄의 부분산화반응에서 La의 효과)

  • Seo, Ho Joon
    • Applied Chemistry for Engineering
    • /
    • v.30 no.6
    • /
    • pp.757-761
    • /
    • 2019
  • The catalytic yields of POM to hydrogen over M(1)-Ni(5)/AlCeO3 (M = La, Ce, Y) were investigated using a fixed bed flow reactor under atmosphere. The crystal phase behavior of reduced La(1)-Ni(5)/AlCeO3 catalysts before and after the reaction were studied via XRD analysis. FESEM and EDS analyses were further performed to show the uniformed distribution of La, Ni, and Ce metal particles on the catalyst surface. XPS results showed O2-, O22- species and metal ions such as Ce3+, Ce4+, La3+ and Ni2+ etc. were on the catalyst surface. When 1 wt% of La was added to Ni(5)/AlCeO3 catalyst, Ni2p3/2 and Ce3d5/2 increased 52.7 and 6.3%, respectively. The yield of hydrogen on the La(1)-Ni(5)/AlCeO3 catalyst was 89.1%, which was much better than that of M(1)-Ni(5)/AlCeO3 (M = Ce, Y). As Ce4+ ions of CeO2 produced by the reaction of AlCeO3 with oxygen were substitute to La3+, it made oxygen vacancies in the lattice and further improved the hydrogen yield by increasing the dispersion of Ni atoms with strong metal-support interaction (SMSI) effect.

Epitaxial Growth of Pulsed-Laser Deposited Bi4Ti3O12/LaAlO3 Thin Films and Bi4Ti3O12/YBa2Cu3O7-x/LaAlO3 Heterostructure (펄스레이저 증착법으로 제작된 $Bi_4Ti_3O_{12}/LaAlO_3$ 박막과 $Bi_4Ti_3O_{12}/YBa_2Cu_3O_{7-x}/LaAlO_3$ 복합구조의 에피 성장)

  • Jo, Wol-Ryeom;Jo, Hak-Ju;No, Tae-Won
    • Korean Journal of Crystallography
    • /
    • v.5 no.2
    • /
    • pp.85-92
    • /
    • 1994
  • Ferroelectric Bi4Ti3012 thin films have been grown on LaAlO(001) by Pulsed-laser deposition. Phase formation and structural films prepared of the films prepared at varigus deposition temperatures are investigated using x-ray diffraction The film grown at 740℃ shows epitaxial growth behavior with c-akis normal to the substrate. N2tBmstiucCures of Bi4Ti3012/YBa2Cu307-x/LaAIO3(001) have been in-situ grown. Even though the a-and b-axes of the Yba2Cu307-x layer show epitaxial growth behavior.

  • PDF

Synthesized and sinteristics of $LaAlO_3$ ceramics from high energy ball milling powders (고에너지 볼밀로 만든 $LaAlO_3$ 분말의 합성과 소결 특성)

  • Chae, Sang-Soo;Seo, Byung-Jun;Chung, Su-Tae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.648-651
    • /
    • 2003
  • Fine $LaAlO_3$ powders were successfully synthesized from $La_2O_3$ and ${\gamma}-Al_2O_3$ powders milling for $10{\sim}50hrs$ via the high energy milling technique (mechanochemical methode) in room temperature and air. The particle size of $LaAlO_3$ powder were estimated from XRD patterns and SEM images to be $160{\sim}180nm$. The $LaAlO_3$ ceramics are derived for the synthesized powders (milling for 10, 30 and 50hrs) by sintering at $1400^{\circ}C$. The micrographs of grains showed a agglomeration and the degree of agglomeration increased with the milling time. The $LaAlO_3$ made from synthesized powders milling for 30hrs can be sintered to 98% of theoretical density at $1,400^{\circ}C$ for 4hrs.

  • PDF

Preparation and Characterization of LaAlO3 Ceramics from High Energy Ball Milling Powders (고에너지 볼 밀에 의한 LaAlO3 세라믹스의 제조와 특성)

  • 최상수;서병준;여기호;정수태
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.17 no.1
    • /
    • pp.39-45
    • /
    • 2004
  • Fine LaAlO$_3$ powders wore successfully synthesized from La$_2$O$_3$ and ${\gamma}$ $Al_2$O$_3$ powders milling for 10∼50 hours via the high energy milling technique (mechanochemical method) in room temperature and air. The particle size of LaAlO$_3$ powder were estimated from XRD patterns and SEM images to be 160∼180 nm. The LaAlO$_3$ ceramics arc derived for the synthesized powders (milling for 10, 30 and 50 hours) by sintering at 140$0^{\circ}C$ and 150$0^{\circ}C$. The micrographs of grains showed an agglomeration and the degree of agglomeration increased with the milling time. The LaAlO$_3$ made from synthesized powders milling for 50 hours can be sintered to 99.5% of theoretical density at 150$0^{\circ}C$ for 1 hour. These ceramics exhibits a dielectric constant of 20, a dielectric loss of 0.0003 and a temperature coefficient of capacitance of 15 ppm/$^{\circ}C$ at 1 MHz.

Effect of Y2O3 and La2O3 on the Sintering Behavior of Alumina (Y2O3 및 La2O3 첨가가 알루미나의 소결거동에 미치는 영향)

  • Lee, Keun Bong;Kang, Jong Bong
    • Korean Journal of Materials Research
    • /
    • v.26 no.2
    • /
    • pp.90-94
    • /
    • 2016
  • In this study, to increase the strength and enhance the sintering property of $Al_2O_3$, $Y_2O_3$ and $La_2O_3$ were added; the effects of these additions on the sintering characteristics of $Al_2O_3$ were observed. Adding 1% of $Y_2O_3$ to $Al_2O_3$ repressed the development of abnormal particles and reduced the grain boundary migration of $Al_2O_3$, curbing pores to capture particles; as such, the material showed a fine microstructure. But, when over 2% of $Y_2O_3$ was added, the sintering property was reduced because of abnormal particle grain growth and pore formation in particles. Adding 1% of $Y_2O_3$ and $La_2O_3$ to $Al_2O_3$ led to the development of abnormal particles and formed pores in the particles; when over 3% of $La_2O_3$ was added, the sintering property was reduced because the shape of the $Al_2O_3$ particles changed to angled plates.

Molecular Beam Epitaxy Grouth of $\textrm{LaAlO}_3$ Thin Film by a Pulsed laser Deposition Technique (펄스레이저증착법을 이용한 $\textrm{LaAlO}_3$ 박막의 Molecular Beam Epitaxy 성장)

  • Kim, In-Seon;Heo, Nam-Hoe;Park, Yong-Gi
    • Korean Journal of Materials Research
    • /
    • v.9 no.1
    • /
    • pp.25-29
    • /
    • 1999
  • We have developed a laser molecular beam epitaxy system for the layer-by-layer growth of oxide thin films. Using this system, we could grow and control oxide thin films of LaAlO$_3$in a molecular layer epitaxy mode on the atomically flat SrTiO$_3$ substrate with a LaAlO$_3$single crystal target. Very clear RHEED oscillations were observed during to growth of a LaAlO$_3$ film for a long period under the optimized conditions of substrate temperature at $650^{\circ}C$, oxygen pressure at 1$\times$10\ulcorner torr, and an incident laser fluence of 4.6J/$\textrm{cm}^2$. The height of mono-layer-LaAlO$_3$ film grown during one period of RHEED intensity oscillation was 3.8$\AA$.

  • PDF