• Title/Summary/Keyword: $Bi_{0.5}K_{0.5}TiO_3$

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Microstructure and PTCR characteristic of high $T_c$ lead-free ((1-x)$BaTiO_3-x(Bi_{1/2}Na_{1/2})TiO_3$ characteristic (High $T_c$ Pb-free (1-x)$BaTiO_3-x(Bi_{1/2}Na_{1/2})TiO_3$ 세라믹의 미세구조와 PTCR 특성)

  • Kim, Chul-Min;Cho, Yong-Soo;Jeong, Young-Hun;Lee, Young-Jin;Lee, Mi-Jae;Paik, Jong-Hoo;Lee, Woo-Young;Kim, Dae-Joon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.32-32
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    • 2008
  • Microstructure and positive temperature coefficient of resistivity (PTCR) characteristics of $0.9BaTiO_3-0.1(Bi_{0.5}Na_{0.5})TiO_3$ [BaBiNT] ceramics doped with $Nb_2O_5$ were investigated in order to develop the Pb-free high Curie temperature ($T_c$)(>$160^{\circ}C$) PTC thermistor. The BaBiNT ceramics showed a tetragonal perovskite structure, irrespective of the added amount of $Nb_2O_5$. They also have a homogeneous microstructure. The resistivity of BaBiNT ceramics was gradually decreased by doping $Nb_2O_5$, which might be due to $Nb^{+5}$ ions substituting for $Ti^{+4}$ sites. The PTCR characteristics of BaBiNT ceramics appeared when the amount of doped $Nb_2O_5$ exceeded 0.0025mol%. Moreover, the abrupt grain growth was observed for the 0.03mol% $Nb_2O_5$added BaBiNT ceramics. It showed an especially high $T_c$ of approximately $172^{\circ}C$ and good PTCR characteristics of a high $\rho_{max}/\rho_{min}$ ratio ($2.96\times10^3$), a high resistivity temperature factor (11.40/$^{\circ}C$) along with a relatively low resistivity ($3.5\times10^4\Omega{\cdot}cm$).

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Structural and Electrical Properties of (Na0.465K0.465Bi0.07)(Nb0.93Ti0.07)O3-0.08MnO2 Ceramics with Variation of Sintering Temperature (소결온도에 따른 (Na0.465K0.465Bi0.07)(Nb0.93Ti0.07)O3-0.08MnO2 세라믹스의 구조적, 전기적 특성)

  • Lee, Tae-Ho;Yeo, Jin-Ho;Lee, Sung-Gap
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.7
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    • pp.506-510
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    • 2012
  • In this study, lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics were fabricated by conventional mixed oxide method. Structural and electrical properties of lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics with the variation of sintering temperature were investigated. As results of x-ray diffraction analysis, all specimens showed a typical polycrystalline perovskite structure without presence of the second phase. Sintered density increased with an increases of sintering temperature and the specimen sintered at $1,020^{\circ}C$ showed the maximum value of 4.5 $g/cm^3$. The average grain size of the $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimen sintered at $1,020^{\circ}C$ is about 0.83 ${\mu}m$. Electromechanical coupling factor, relative dielectric constant and dielectric loss of $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimens sintered at $1,020^{\circ}C$ were 0.252, 741 and 0.043% respectively.

Preparation of Bi0.5Na0.5TiO3-Based Multilayer Ceramic Actuators Using Microwave Sintering (마이크로파 소결법을 이용한 Bi0.5Na0.5TiO3계 적층형 세라믹 액추에이터 제조)

  • Kang, Jin-Kyu;Lee, Jae-Shin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.11
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    • pp.702-706
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    • 2014
  • A comparative study has been attempted for microwave and conventional sintering of lead-free $Bi_{0.5}Na_{0.5}TiO_3(BNT)$-based multilayer ceramic actuators(MLAs). It was found that microwave sintering (MWS) could be successfully applied to the co-firing of piezoceramic/AgPd MLAs with a 10 times shorter firing cycle as well as $100^{\circ}C$ lower firing temperature ($850^{\circ}C$) for sufficient densification than conventional furnace sintering ($950^{\circ}C$). Furthermore, MWS-derived specimens showed better electric field-induced strain than that of CFS-derived specimens by effectively suppressing interdiffusions between ceramic and electrode layers.

The effect of nano-sized starting materials and excess amount of Bi on the dielectric/piezoelectric properties of 0.94[(BixNa0.5)TiO3]-0.06[BaTiO3] lead free piezoelectric ceramics

  • Khansur, Neamul Hayet;Ur, Soon-Chul;Yoon, Man-Soon
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2009.11a
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    • pp.31.1-31.1
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    • 2009
  • In an approach to acclimate ourselves torecent ecological consciousness trend, a lead-free piezoelectric material, bismuth sodium titanate (abbreviated as BNT) based bismuth sodium barium titanate (abbreviated as BNT-BT), was considered as an environment-friendly alternative for a lead based piezoelectric system. Ceramic specimens of0.94[(BixNa0.5)TiO3]-0.06[BaTiO3] (x = 0.500~0.515) compositions were prepared by a modified mixed oxide method. To increase the chemical homogeneity andre action activity, high energy mechanical milling machine and pre-milled nanosized powder has been used. In this method (BixNa0.5)TiO3 (x=0.500~0.515) andBaTiO3 were prepared separately from pre-milled constituent materials at low calcination temperature and then separately prepared BNTX (X=1, 2, 3 and 4) and BT were mixed by high energy mechanical milling machine. Without further calcination step the mixed powders were pressed into disk shape and sintered at $1110^{\circ}C$. Microstructures, phase structures and electrical properties of the ceramic specimens were systematically investigated. Highly dense ceramic specimens with homogenous grains were prepared in spite of relatively low sintering temperature. Phase structures were not significantly influenced by the excess amount Bi. Large variation on the piezoelectric and dielectric properties was detected at relative high excess Bi amounts. When $x{\leq}0.505$, the specimens exhibit insignificant variation in piezoelectric and dielectric constant though depolarization temperature is found to be decreased. Considerable amount of decrease in piezoelectric and dielectric properties are observed with higher excess of Bi amounts ($x{\geq}0.505$). This research indicates the advantages of high energy mechanical milling and importance of proper maintenance of Bi stoichiometry.

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Electrocaloric Effect of (Bi0.5Na0.5)TiO3 Ceramics ((Bi0.5Na0.5)TiO3 세라믹스의 유전 및 전기열량 특성)

  • Han, Jong-Dae;Yoo, Ju-Hyun;Jeong, Yeong-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.5
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    • pp.284-287
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    • 2017
  • The electrocaloric effect in $0.94(Bi_{0.5}Na_{0.5})TiO_3+0.06KNbO3+0.9wt%$ G.F.ferroelectricceramics was observed in terms of the temperature change (${\Delta}T$) of the fabricated ceramics, Curie temperature $T_c$, and applied electric field. The specimens were fabricated by a conventional solid-state reaction. $T_c$ appeared near $165{\sim}170^{\circ}C$. The P-E hysteresis showed a tendency to slim down with a temperature increase and finally was slimmest near $150^{\circ}C$. With the increase of temperature, the polarization revealed a gradual decrease, and a sharp decline near $T_c$. When an electric field of 45 kV/cm was applied, the largest polarization was shown. The maximum value of the temperature change (${\Delta}T=0.31^{\circ}C$) was obtained at $165^{\circ}C$ under an applied electric field of 45 kV/cm.

Effects of Sodium Excess on Ferroelectric Properties of Bi0.5(Na0.78K0.22)0.5TiO3 Ceramics (Bi0.5(Na0.78K0.22)0.5TiO3 세라믹스의 강유전 특성에 미치는 나트륨 과잉 효과)

  • Park, Jung-Soo;Kim, Seong-Won;Jeong, Young-Hun;Yun, Ji-Sun;Paik, Jong-Hoo;Lee, Sung-Gap;Cho, Jeong-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.12
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    • pp.764-768
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    • 2016
  • To investigate excess $Na^+$ effect, $Bi_{0.5}(Na_{0.78+x}K_{0.22})_{0.5}TiO_3$ ($0{\leq}x{\leq}0.05$) (BNKT) ceramics were prepared by using a conventional solid-state reaction method. The structure and ferroelectric properties of BNKT ceramics were characterized by XRD (X-ray diffraction) and polarization dependence by external electric field. Also, the temperature dependence of dielectric constant and loss were studied. From these results, it was found that appropriate excess $Na^+$ into BNKT ceramics compensate the volatility and induce dense ceramics. The enhanced piezoelectric coefficient (158 pC/N) and depolarization temperature ($202^{\circ}C$) were obtained for the x=0.01 composition.

Synthesis of High-Aspect-Ratio BaTiO3 Platelets by Topochemical Conversion and Fabrication of Textured Pb(Mg1/3Nb2/3)O3-32.5PbTiO3 Ceramics

  • Zhao, Wei;E, Lei;Ya, Jing;Liu, Zhifeng;Zhou, Heping
    • Bulletin of the Korean Chemical Society
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    • v.33 no.7
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    • pp.2305-2308
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    • 2012
  • Perovskite structured barium titanate particles ($BaTiO_3$) platelets were synthesized by molten salt synthesis and topochemical microcrystal conversion. As the precursors of $BaTiO_3$, plate-like $BaBi_4Ti_4O_{15}$ particles were first synthesized by the reaction of $Bi_4Ti_3O_{12}$, $BaCO_3$, and $TiO_2$ at $1080^{\circ}C$ for 3 h in $BaCl_2$-KCl molten salt. After the topochemical reactions, layer-structured $BaBi_4Ti_4O_{15}$ particles transformed to the perovskite $BaTiO_3$ platelets. $BaTiO_3$ particles with thickness of approximately $0.5{\mu}m$ and a length of $10-15{\mu}m$ retained the morphology feature of the $BaBi_4Ti_4O_{15}$ precursor. For <001> $Pb(Mg_{1/3}Nb_{2/3})O_3-32.5PbTiO_3$ (PMNT)-5 wt % PbO piezoelectric ceramics textured with 5 vol % of $BaTiO_3$ templates, the Lotgering factor reached 0.82, and $d_{33}$ was 870 pC/N.

Effects of substitution with La and V in $Bi_4Ti_3O_{12}$ thin film by MOCVD using ultrasonic spraying (초음파분무 MOCVD법에 의한 $Bi_4Ti_3O_{12}$ 박막의 제조와 La과 V의 Co-Substitution 에 의한 효과)

  • 김기현;곽병오;이승엽;이진홍;박병옥
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.13 no.6
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    • pp.272-278
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    • 2003
  • $Bi_4Ti_3O_{12}$ (BIT) and $(Bi_{3.25}La_{0.75})(Ti_{2.97}V_{0.03})O_{12}$ (BLTV) thin films were deposited on ITO/glass substrates by metal organic chemical vapor deposition (MOCVD) using ultrasonic spraying. After deposition of the films in oxygen atmosphere for 30 min, the films were heated by rapid thermal annealing (RTA) method, especially direct insertion, at various temperatures. The films were investigated on phase formation temperature, microstructure and electrical properties. From x-ray diffraction (XRD) patterns, the perovskite phase formation temperature of BLTV thin film was about $600^{\circ}C$ which was lower than that of BIT, $650^{\circ}C$. The leakage current of the BLTV thin film was measured to be $1.52\times 10^{-9}$A/$cm^2$ at an applied voltage of 1 V. The remanent polarization (Pr) and coercive field (Ec) values of the BLTV film deposited at $650^{\circ}C$ were $5.6\muC/cm^2$ and 96.5 kV/cm, respectively.

Effect of $BaTiO_3$ according to $(Bi_{0.5}Na_{0.5})TiO_3$ for Pb-free PTC (Pb-free PTC에 있어서 $(Bi_{0.5}Na_{0.5})TiO_3$ 첨가에 따른 $BaTiO_3$ 효과)

  • Lee, Mi-Jai;Paik, Jong-Hoo;Kim, Sei-Ki;Kim, Bip-Nam;Lee, Woo-Yong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.57-58
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    • 2008
  • PTC thermistor are characterized by an increase in the electrical resistance with temperature. The PTC materials of middle Curie point were produced or that of high Curie point (above $200^{\circ}C$), it was determined that compositional modifications of $Pb^{2+}$ for $Ba^{2+}$ produce change sin the Curie point to higher temperature. PTC ceramic materials with the Curie point above $120^{\circ}C$ were prepared by adding $PbTiO_3$, PbO or $Pb_3O_4$ into $BaTiO_3$. Thereby, adding $Pb^{2+}$ into $BaTiO_3$-based PTC material to improve Tc was studied broadly, however, weal know that PbO was poisonous and prone to volatilize, then to pollute the circumstance and hurt to people, so we should dope other innocuous additives instead of lead to increase Tc of composite PTC material. In order to prepare lead-free $BaTiO_3$-based PTC with middle Curie point, the incorporation on $Bi_{1/2}Na_{1/2}TiO_3$ into $BaTiO_3$-based ceramics was investigated on samples containing 0, 1, 2, 3, 4, and 50mol% of $Bi_{1/2}Na_{1/2}TiO_3$. $Bi_{1/2}Na_{1/2}TiO_3$ was compounded as standby material by conventional solid-state reaction technique. The starting materials were $Bi_{1/2}Na_{1/2}TiO_3$, $BaCO_3$, $TiO_2$ and $Y_2O_3$ powder, and using solid-state reaction method, too. The microstructures of samples were investigated by SEM, DSC, XRD and dielectric properties. Phase composition and lattice parameters were investigated by X-ray diffraction.

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