• Title, Summary, Keyword: $BaTiO_3$

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Preparation of $BaTiO_3$ powder in solid reaction and basic study on dielectrics of $CeAIO_3-BaTiO_3$system ($BaTiO_3$ 분말합성조건 및 $CeAIO_3-BaTiO_3$계 유전체의 기초적 연구)

  • Lim, Dae-Young;Kim, Jong-Ock;Lee, Chae-hyun;Park, Won-Kyu
    • The Journal of Natural Sciences
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    • v.8 no.1
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    • pp.61-69
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    • 1995
  • It is hard to synthesize pure $BaTiO_3$ from $BaCO_3$ and $TiO_2$ in solid reaction for the activity of BaO and secondary phase. For this reason, the wet chemical techniques have been studied. Starting material which was used in these methods were expensive and the properties of powder which was synthesized in same defined. So, some process have been studying again to improve soild reaction method. This study which was one of those was to defin the forming mechanism of $Ba_2TiO_4$ and to control some condition of $Ba_2TiO_4$. The synthesis temperature of $BaTiO_3$ in solid reaction was near $1120^{\circ}C$. The quantity and forming temperature of $Ba_2TiO_4$ could be controlled by atmosphere heat treatment. $Ba_2TiO_4$ was related to expansion in Ba-rich region of $BaTiO_3$. $BaTiO_2O_5$ and $BaTiO_3O_7$ was reason to expand in Ti-rich region. The dielectrics of $CeAIO_3$ which was synthesized and sintered in reduction atmosphere and $BaTiO_3$ system were affected by $CeO_2$ which was formed for the decomposition of $CeAIO_3$ heat treatment in air.

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The Dielectric Properties of $BaTiO_3/SrTiO_3$ Heterolayered Thick Films with Stacking Periodicity (적층주기에 따른 $BaTiO_3/SrTiO_3$ 이종층 후막의 유전 특성)

  • Lee, Yoe-Bok;Choi, Eui-Sun;Lee, Moon-Kee;Ryu, Ki-Won;Lee, Young-Hie
    • Proceedings of the KIEE Conference
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    • pp.194-196
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    • 2004
  • $BaTiO_3/SrTiO_3$ heterolayered thick films on the $Al_2O_3$ substrate by screen printing method with stacking periodicity. The stacking periodicity of $BaTiO_3/SrTiO_3$ heterolayer structure was varied from $(BaTi_O_3)_1/(SrTiO_3)_1$ to $(BaTi_O_3)_3/(SrTiO_3)_3$. The total thickness of the $BaTiO_3/SrTiO_3$ films was about $120{\mu}m$. There was an interdiffusion at the interface of the $BaTiO_3$ and $SrTiO_3$ layers. The dielectric constant of $BaTiO_3/SrTiO_3$ heterolayered thick films was increased with decreasing stacking periodicity of the $BaTiO_3/SrTiO_3$. The dielectric constant of the ($(BaTi_O_3)_1/(SrTiO_3)_1$ herterolayered thick films was about 1780.

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Stable Defect Structure of La2O3-Modified BaTiO3 (La$_2O_3$-변형 BaTi$O_3$의 안정한 결함구조)

  • Kim, Jeong Su;Park, Hyu Beom;An, Tae Ho;Kim, Si Jung
    • Journal of the Korean Chemical Society
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    • v.38 no.4
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    • pp.309-318
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    • 1994
  • The stable defect structure and the single phase region of La$_2O_3$-modified BaTi$O_3$ have been studied by X-ray diffractometer and scanning electron microscope. The stable defect structure of La$_2O_3$-modified BaTi$O_3$ has been identified as [($Ba^x_{Ba})_{1-2x}(La{\cdot}_{Ba})_{2x}][Ti^x_{Ti})_{1-x/2}(V""_{Ti})_{x/2}]O_3$ which consists of La$^{3+}$ ion substitution for Ba$^{3+}$ ion in the lattice structure and the formation of Ti vacancies for the charge compensation. When 3 mol% of La$_2O_3{\cdot}3/2TiO_3$ was added to BaTi$O_3$, the unit cell structure was transformed from tetragonal to cubic and the solubility limit was about 14 mol%. When La$_2O_3{\cdot}3/2TiO_2$ was added above this solubility limit, the second phase, La$_4Ba_2Ti_5O_{18}$, was formed. In the La$_2O_3$-modified BaTi$O_3$, it was found by the liquid phase sintering process that the sinterability was decreased by excess BaO but increased by excess Ti$O_2$.

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A Study on Solid Reaction of BaCO3-TiO2 System (BaCO3-TiO2계의 고상반응에 관한 연구)

  • 이응상;황성연;임대영
    • Journal of the Korean Ceramic Society
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    • v.24 no.5
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    • pp.484-490
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    • 1987
  • Diffusion coupling experiment was done to study expansion of body and soild reaction in BaCO3-TiO2 system. Specimen of BaCO3 and TiO2 was formed with Pt-mark's method. Each specimen was fired at interval of 25℃ from 900℃ to 1000℃ for 2hrs. After that, specimen was fixed with resin and polished. Product layers of specimen were observed with SEM and EDS. The result were following; 1. Diffusion component is Ba2+, which diffuse toward TiO2. 2. Large crack between layer of BaCO3 and Ba2TiO4 was generated because of difference of thermal expansion coefficient. 3. Ba2TiO4 is formed to TiO2 body by the reaction of BaTiO3 and BaO and its structure is very porous. 4. BaTiO3 changes immediately to Ba2TiO4 by the reaction of BaO. But BaTiO3 which formed by the reaction of TiO2 and Ba2TiO4 exsists as layer because the diffusion distance of Ba2+ is far.

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The Complexing Effect of $BaTiO_3\;for\;Bi_4Ti_3O_{12}$ on Layered Perovskite $Bi_4Ti_3O_{12}{\cdot}nBaTiO_3(n=1&2)$ Thin Films ($Bi_4Ti_3O_{12}{\cdot}nBaTiO_3(n=1&2)$ 박막에서 $Bi_4Ti_3O_{12}$ 에 대한 $BaTiO_3$의 복합효과)

  • 신정묵;고태경
    • Journal of the Korean Ceramic Society
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    • v.35 no.11
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    • pp.1130-1140
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    • 1998
  • Thin films of $Bi_4Ti_3O_{12}\;nBaTiO_3(n=1&2)$ were prepared using sols erived Ba-Bi-Ti complex alkoxides. The sols were spin-cast onto $Pt/Ti/SiO_2/Si$ substrates and followed by pyrolysis for 1 hr at $620^{\circ}C,\;700^{\circ}C\;and\;750^{\circ}C$ In the thin films a pyrochlore phase seemed to be formed at a lower temperature and then tran-formed to the layered perovskite phase as the heating temperature increased. In the thin films pyrolyzed at formed to the layered perovskte phase as the heating temperature increased. In the films pyrolyzed at $750^{\circ}C$ the amount of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ reached to 94% while $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ was 77% in composition. This result shows that the formation of the layered pervoskite phase becomes difficult as the amount of complexing $BaTiO_3$ increases. The microstructures and the electrical properties of the thin films were gen-erally improved with the incease of the heating temperature. However the presence of the pyrochlore phase could not be removed effectively. Our study showed that the electrical properties of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ were pronouncedly improved with complexing with BaTiO3 when compared to those of $Bi_4Ti_3O_{12}$ while the presence of the pyrochlore phase was detrimental to the those of $Bi_4Ti_3O_{12}{\cdot}2BaTiO_3$.

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A Study of the Synthesis and the Properties on Microwave Dielectric Material of BaO-Pr$_2$O$_3$-TiO$_2$ and BaO-(Nd,Pr)$_2$O$_3$-TiO$_2$ System (BaO-Pr$_2$O$_3$-TiO$_2$계 및 BaO-(Nd,Pr)$_2$O$_3$-TiO$_2$계 마이크로파 유전체의 합성 및 특성에 관한 연구)

  • 이용석;이재원;성학제;김준수;이병하
    • Journal of the Korean Ceramic Society
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    • v.35 no.8
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    • pp.775-782
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    • 1998
  • This experiment is third study concerning BaO-{{{{ { { Pr}_{ 2} O}_{3 } }}-{{{{ { TiO}_{2 } }} (Ln=Sm, Nd, Pr, La..) system which is known to show a high dielectric constant and Q value in microwave dielectric materials. The process of cry-stallization and the microwave dielectric properties of the specimens sintered at 1220-140$0^{\circ}C$ for 2 hr was investigated in the BaO-(Na,{{{{ { { Pr})_{2 }O }_{3 } }}-{{{{ { TiO}_{2 } }} as well as BaO-{{{{ { { Pr}_{ 2} O}_{3 } }}-{{{{ { TiO}_{2 } }} system. The single phase BaPr2Ti5O14 and Ba(Nd,{{{{ { { Pr})_{2 }O }_{3 } }}Ti5O14 was finally formed from the Pr2Ti2O7 (Nd, Pr)2Ti2O7 as a secondary phase in the BaO-{{{{ { { Pr}_{ 2} O}_{3 } }}-{{{{ { TiO}_{2 } }} and BaO-(Nd, {{{{ { { Pr})_{2 }O }_{3 } }}-{{{{ { TiO}_{2 } }} system respectively The dielectric constant of the specimens sint-ered at 1280~131$0^{\circ}C$ showed the maximum value as 105(BaO-{{{{ { { Pr}_{ 2} O}_{3 } }}-{{{{ { TiO}_{2 } }} system) and 88 (BaO-(Nd,{{{{ { { Pr})_{2 }O }_{3 } }}-{{{{ { TiO}_{2 } }} system) and the Q values of them showed higher value than 1800 which are due to the maximum den-sity. However the dielectric properties of the specimens sintered at higher temperature than 131$0^{\circ}C$ were reduced due to the increases of pore which were resulted from the sudden grain growth.

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A Study of the synthesis and the properties on microwave dielectric material of BaO--$Nd_2O_3$-$TiO_2$and BaO-(Sm, $ND)_2O_3$-$TiO_2$ system (BaO-$Nd_2O_3$-$TiO_2$계 및 BaO-(Sm, $ND)_2O_3$-$TiO_2$계 마이크로파 유전체의 합성 및 제특성에 관한 연구)

  • 이용석;김준수;이병하
    • Electrical & Electronic Materials
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    • v.10 no.8
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    • pp.819-829
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    • 1997
  • The microwave dielectric materials of the BaO-Nd$_2$O$_3$-TiO$_2$and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system were synthesized by conventional ceramic processing and sintered 1220 to 140$0^{\circ}C$ for 2 hours respectively. Their crystallization and dielectric properties were examined. In the BaO-Nd$_2$O$_3$-TiO$_2$ and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system. Nd$_2$Ti$_2$O$_{7}$ and (Sm, Nd)$_2$Ti$_2$O$_{7}$ were observed as a second phase respectively. The maximum relative dielectric constant were 79,99 for the BaO-Nd$_2$O$_3$-TiO$_2$system and 105.07 for the BaO-(Sm,Nd)$_2$O$_3$-TiO$_2$system and their Q-value were over 2000 at 3GHz.GHz.

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Hydrothermal synthesis of $BaTiO_3$ fine particles (수열법에 의한 $BaTiO_3$ 미립자의 합성)

  • 최종건;김판채
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.8 no.1
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    • pp.49-54
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    • 1998
  • $BaTiO_3$ fine particles were synthesized by hydrothermal method. $TiO_2$ and $Ba(OH)_2{\cdot}8H_2O$ were used as staring materials, and it was possible to synthesize $BaTiO_3$ fine particles in pure water by using excess $Ba(OH)_2{\cdot}8H_2O$. The shape of synthesized particles are irregular but near spherical, and the particle size depends on the temperature and Ba/Ti atomic ratio.

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The Dielectric Properties of $BaTiO_3/SrTiO_3$ Heterolayered Thick Films ($BaTiO_3/SrTiO_3$ 이종층 후막의 유전특성)

  • Nam, Sung-Pill;Lee, Sang-Chul;Lee, Sung-Gap;Lee, Young-Hie
    • Proceedings of the KIEE Conference
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    • pp.58-60
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    • 2004
  • The $BaTiO_3/SrTiO_3$ heterolayered thick films were fabricated on alumina substrate by screening printing method. The obtained films were sintered at $1400^{\circ}C$ with bottom electrode of Pt for 2 hours. The structural and electrical properties of $BaTiO_3/SrTiO_3$ heterolayered thick films were compared with pure $BaTiO_3$ and $SrTiO_3$ films. The (Ba,Sr)$TiO_3$ phase was appeared at the $BaTiO_3/SrTiO_3$ heterolayered thick films. The thickness of $BaTiO_3/SrTiO_3$ heterolayered thick film, obtained by one printing, was about $50{\mu}m$. The dielectric constant and dielectric loss of the $BaTiO_3/SrTiO_3$ heterolayered thick films were about 1964, 5.5% at 1KHz, respectively.

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Characteristics of Amorphous/Polycrystalline $BaTiO_3$ Double Layer Thin Films with High Performance Prepared New Stacking Method and its Application to AC TFEL Device (새로운 적층방법으로 제조된 고품위 비정질/다결정 $BaTiO_3$ 적층박막의 특성과 교류 구동형 박막 전기 발광소자에의 응용)

  • 송만호;이윤희;한택상;오명환;윤기현
    • Journal of the Korean Ceramic Society
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    • v.32 no.7
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    • pp.761-768
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    • 1995
  • Double layered BaTiO3 thin films with high dielectric constant as well as good insulating property were prepared for the application to low voltage driving thin film electroluminescent (TFEL) device. BaTiO3 thin films were formed by rf-magnetron sputtering technique. Amorphous and polycrystalline BaTiO3 thin films were deposited at the substrate temperatures of room temperature and 55$0^{\circ}C$, respectively. Two kinds of films prepared under these conditions showed high resistivity and high dielectric constant. The figure of merit (=$\varepsilon$r$\times$Eb.d) of polycrystalline BaTiO3 thin film was very high (8.43$\mu$C/$\textrm{cm}^2$). The polycrystalline BaTiO3 showed a substantial amount of leakage current (I), under the high electric field above 0.5 MV/cm. The double layered BaTiO3 thin film, i.e., amorphous BaTiO3 layer coated polycrystalline BaTiO3 thin film, was prepared by the new stacking method and showed very good dielectric and insulating properties. It showed a high dielectric constant fo 95 and leakage current density of 25 nA/$\textrm{cm}^2$ (0.3MV/cm) with the figure of merit of 20$\mu$C/$\textrm{cm}^2$. The leakage current density in the double layered BaTiO3 was much smaller than that in polycrystalline BaTiO3 under the high electric field. The saturated brightness of the devices using double layered BaTiO3 was about 220cd/$m^2$. Threshold voltage of TFEL devices fabricated on double layered BaTiO3 decreased by 50V compared to the EL devices fabricated on amorphous BaTiO3.

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