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

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Fabrication and Characterization of (1-x)BiFeO3-xBaTiO3 Ceramics Prepared by a Solid State Reaction Method

  • Chandarak, S.;Unruan, M.;Sareein, T.;Ngamjarurojana, A.;Maensiri, S.;Laoratanakul, P.;Ananta, S.;Yimnirun, R.
    • Journal of Magnetics
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    • v.14 no.3
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    • pp.120-123
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    • 2009
  • In this study, BiFe$O_3$-BaTi$O_3$ ceramics have been fabricated by a solid-state reaction method. The effects of BaTi$O_3$ content in the (1-x)BiFe$O_3$-xBaTi$O_3$ (x = 0.1, 0.2, 0.25, 0.3, 0.4, 0.5) system on crystal structure and magnetic, dielectric, and ferroelectric properties were investigated. Perovskite BiFe$O_3$ was stabilized through the formation of a solid solution with BaTi$O_3$. Rhombohedrally distorted structure (1-x)BiFe$O_3$-xBaTi$O_3$ ceramics showed strong ferromagnetism at x = 0.5. Dielectric and ferroelectric properties of the BiFe$O_3$-BaTi$O_3$ system also changed significantly upon addition of BaTi$O_3$. It was found that the maximum dielectric and ferroelectric properties were exhibited in the (1-x)BiFe$O_3$-xBaTi$O_3$ system at x = 0.25. This suggested the morphotropic phase boundary (MPB) with the coexistence of both rhombohedral and cubic phases of the (1-x)BiFe$O_3$-xBaTi$O_3$ system at x = 0.25.

Dielectric and Piezoelectric Properties of Lead-free (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3 Ceramics (비납계 (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3 세라믹의 유전 및 압전 특성)

  • Cho J. A.;Kuk M.-H.;Sung Y. S.;Lee S. H.;Song T. K.;Jeong S. J.;Song J. S.;Kim M.-H.
    • Korean Journal of Materials Research
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    • v.15 no.10
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    • pp.639-643
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    • 2005
  • Lead-free $[Bi_{0.5}(Na_{1-x}K_x)_{0.5}TiO_3](x=0\~1.0)$ ceramics were prepared using a solid state reaction method and their structural and electrical characteristics were investigated. X-ray investigations indicated that the rhombohedral-tetragonal morphotropic phase boundary(MPB) of the $[Bi_{0.5}(Na_{1-x}K_x)TiO_3$ ceramics exists in the range of $x=0.16\~0.20$. The optimum values of piezoelectric constant$(d_{33})$, dielectric constant, and electromechanical coupling factor $(k_p)$ were obtained at $x=0.16\~0.20$ of the MPB region.

Microstructure and PTCR Behavior of Semiconducting (1-x)$BaTiO_3$ - x$(Bi_{1/2}K_{1/2})TiO_3$ Ceramics ($BaTiO_3$ - $(Bi_{0.5}Ko_{0.5})TiO_3$계 세라믹의 PTC효과와 미세구조)

  • Park, Yong-Jun;Jeong, Young-Hun;Lee, Young-Jin;Paik, Jong-Hoo;Kim, Dae-Joon;Lee, Woo-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.336-336
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    • 2008
  • A positive temperature coefficient of electrical resistivity (PTCR) was investigated in a ferroelectric lead-free perovskite-type compound $(Bi_{0.5}K_{0.5})TiO_3$ within $BaTiO_3$-based solid solution ceramics. The electrical properties and the microstructure of (1-x) $BaTiO_3$ - x $(Bi_{0.5}K_{0.5})TiO_3$ (BBKT) ceramics made using a conventional mixed and have been synthesized by an ordinary sintering technique. The Curie temperature was obviously increased with increasing of $(Bi_{0.5}K_{0.5})TiO_3$ content. The BKT ceramics (x=0.05) sintered at $1400^{\circ}C$ for 4h display low resistivity values of $10^1-10^2$ ohm cm at room temperature, PTCR effect(jump) of 1.05*$10^3$, and the Curie temperature of $T_c=141^{\circ}C$.

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The structural properties of the (Bi,Ba,Sr)$TiO_3$[BBST] thin films with Ar/$O_2$ rates (Ar/$O_2$비에 따른 (Bi,Ba,Sr)$TiO_3$[BBST] 박막의 구조적 특성)

  • Kim, Jung-Tae;Lee, Sang-Chul;Lee, Sung-Gap;Bae, Seon-Ki;Lee, Young-Hie
    • Proceedings of the KIEE Conference
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    • 2002.07c
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    • pp.1488-1490
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    • 2002
  • The (Bi,Ba,Sr)$TiO_3$[BBST] thin films were fabricated on Pt/Ti/$SiO_2$/Si substrate by RF sputtering method. We investigated the effects of Ar/$O_2$ rates on the structural properties of BBST thin films. Decreasing the $O_2$ rates, the intensity of $BaBi_4Ti_4O_{15}$ and $Bi_4Ti_3O_{12}$ peaks were increased but the $(Ba_{0.5}Sr_{0.5})TiO_3$ peak was decreased. In the case of BBST thin films deposited with condition of 90/10 (Ar/$O_2$) ratio, the composition of Ba/Sr/Bi was 0.35/0.4/0.25. Also, in the BBST thin films deposited with condition of 80/20(Ar/$O_2$) ratio, the composition of Br,Sr and Ti were relatively uniform. But the component of Bi and Ti were diffused into the Pt layers.

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Microwave Dielectric Properties in Bi-Substituted BaO.$Nd_{2}O_{3}$.$4TiO_{2}$ (Bi 가 치환된 BaO.$Nd_{2}O_{3}$.$4TiO_{2}$ 세라믹스의 마이트로파 유전특성)

  • Cheon, Jae-Il;Kim, Jeong-SeoG
    • Korean Journal of Materials Research
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    • v.8 no.7
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    • pp.659-663
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    • 1998
  • The effect of Bi-substitution in $BaO.(Nd_{1-x}Bi_x)_2O_3.4TiO_2$ ceramic was studied on the formation of crystal phases, microstructure, and microwave dielectric properties. $BaO.(Nd_{1-x}Bi_x)_2O_3.4TiO_2$, solid solution (0$\leq$x$\leq$0.2) were formed by Bi-substitution into the Nd site of $BaO.(Nd_{1-x}Bi_x)_2O_3.4TiO_2$ ceramics. Average grain size increased with Bi-substitution. Dielectric constant(${\varepsilon}_r$) increased from 84 to U8, and the temperature coefficient of resonant frequency(${\tau}_f$) decreased from 44 ppm/$^{\circ}C$ to -30 ppm/$^{\circ}C$ when Bi contents increased up to x=0.2 in $BaO.(Nd_{1-x}Bi_x)_2O_3.4TiO_2$ solid solutions. $BaO.(Nd_{1-x}Bi_x)_2O_3.4TiO_2$ solid solutions with x=0.04~0.08 showed the most superior microwave dielectric properties, those are ${\varepsilon}_r$= 89-92, Q . f = 5855~6091 GHz, and (${\tau}_f$)= -7.5-7.5 ppm/$^{\circ}C$.

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Microstructure and Positive Temperature Coefficient of Resistivity Characteristics of Na2Ti6O13-Doped 0.94BaTiO33-0.06(Bi0.5Na0.5)TiO3 Ceramics (Na2Ti6O13를 도핑한 0.94BaTiO3-0.06(Bi0.5Na0.5)TiO3 세라믹스의 미세구조와 Positive Temperature Coefficient of Resistivity 특성)

  • Cha, Yu-Joung;Jeong, Young-Hun;Lee, Young-Jin;Paik, Jong-Hoo;Lee, Wu-Young;Kim, Dae-Joon
    • Korean Journal of Materials Research
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    • v.20 no.11
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    • pp.575-580
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    • 2010
  • The microstructure and positive temperature coefficient of resistivity (PTCR) characteristics of 0.1 mol%$Na_2Ti_6O_{13}$ doped $0.94BaTiO_3-0.06(Bi_{0.5}Na_{0.5})TiO_3$ (BBNT-NT001) ceramics sintered at various temperatures from $1200^{\circ}C$ to $1350^{\circ}C$ were investigated in order to develop eco-friendly PTCR thermistors with a high Curie temperature ($T_C$). Resulting thermistors showed a perovskite structure with a tetragonal symmetry. When sintered at $1200^{\circ}C$, the specimen had a uniform microstructure with small grains. However, abnormally grown grains started to appear at $1250^{\circ}C$ and a homogeneous microstructure with large grains was exhibited when the sintering temperature reached $1325^{\circ}C$. When the temperature exceeded $1325^{\circ}C$, the grain growth was inhibited due to the numerous nucleation sites generated at the extremely high temperature. It is considered that $Na_2Ti_6O_{13}$ is responsible for the grain growth of the $0.94BaTiO_3-0.06(Bi_{0.5}Na_{0.5})TiO_3$) ceramics by forming a liquid phase during the sintering at around $1300^{\circ}C$. The grain growth of the BBNT-NT001 ceramics was significantly correlated with a decrease of resistivity. All the specimens were observed to have PTCR characteristics except for the sample sintered at $1200^{\circ}C$. The BBNT-NT001 ceramics had significantly decreased $\tilde{n}_{rt}$ and increased resistivity jump with increasing sintering temperature at from $1200^{\circ}C$ to $1325^{\circ}C$. Especially, the BBNT-NT001 ceramics sintered at $1325^{\circ}C$ exhibited superior PTCR characteristics of low resistivity at room temperature ($122\;{\Omega}{\cdot}cm$), high resistivity jump ($1.28{\times}10^4$), high resistivity temperature factor (20.4%/$^{\circ}C$), and a high Tc of $157.9^{\circ}C$.

Structure and Dielectric properties of BST Thin Films prepared by Sol-gel method for Tunable element application (Tunable 소자 응용을 위한 Sol-gel 법으로 제작된 BST 박막의 Bi 첨가에 따른 구조적, 유전적 특성)

  • Kim, Tae-Hyung;Kim, Kyoung-Tae;Kim, Chang-Il
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07b
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    • pp.565-568
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    • 2004
  • An alkoxide-based sol-gel method was used to fabricate $Ba_{0.6}Sr_{0.4}TiO_3$ thin films doped by Bi from 5 to 20 mol% on a Pt/Ti/SiO2/Si substrate. The structural and dielectric properties of BST thin films were investigated as a function of Bi dopant concentration. The dielectric properties of the Bi doped BST films were strongly dependent on the Bi contents. The dielectric constant and dielectric loss of the films decreased with increasing Bi content. However, the leakage current density of the 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin film showed the lowest value of 5.13 10-7 at 5 V. The figure of merit (FOM) reached a maximum value of 32.42 at a 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin films. The dielectric constant, loss factor, and tunability of the 10 mol% Bi doped $BBa_{0.6}Sr_{0.4}TiO_3$ thin films were 333,0.0095, and 31.1%, respectively.

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Fabrication of BST thin films with Bi addition by Sol-gel method and their Structure and Dielectric properties (Sol-gel 법으로 제작된 BST 박막의 Bi 첨가에 따른 구조적, 유전적 특성)

  • Kim, Kyoung-Tae;Kim, Chang-Il
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.04b
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    • pp.18-21
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    • 2004
  • An alkoxide-based sol-gel method was used to fabricate $Ba_{0.6}Sr_{0.4}TiO_3$ thin films doped by Bi from 5 to 20 mol% on a $Pt/Ti/SiO_2/Si$ substrate. The structural and dielectric properties of BST thin films were investigated as a function of Bi dopant concentration. The dielectric properties of the Bi doped BST films were strongly dependent on the Bi contents. The dielectric constant and dielectric loss of the films decreased with increasing Bi content. However, the leakage current density of the 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin film showed the lowest value of $5.13{\times}10^{-7}\;A/cm^2$ at 5 V. The figure of merit (FOM) reached a maximum value of 32.42 at a 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin films. The dielectric constant, loss factor, and tunability of the 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin films were 333, 0.0095, and 31.1%, respectively.

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