• Title/Summary/Keyword: $Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3$ Ceramics

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Effects of A-site Vacancies on the Piezoelectric Properties of 0.97Bi0.5+x(Na0.78K0.22)0.5-3xTiO3-0.03LaFeO3 Lead-free Piezoelectric Ceramics (A-site Vacancy가 0.97Bi0.5+x(Na0.78K0.22)0.5-3xTiO3-0.03LaFeO3 무연압전 세라믹스의 압전특성에 미치는 영향)

  • Park, Jung Soo;Lee, Ku Tak;Cho, Jeong Ho;Jeong, Young Hun;Paik, Jong Hoo;Yun, Ji Sun
    • Journal of the Korean Ceramic Society
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    • v.51 no.6
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    • pp.527-532
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    • 2014
  • $0.97Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3-0.03LaFeO_3$ lead-free piezoelectric ceramics were fabricated by a solid state reaction method. $LaFeO_3$ additives were added to $Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3$ for volatile compensation of bismuth and sodium ions in the sintering process. To create A-site vacancies, the mole ratio and charge valence of A-site ions ($Bi^{3+}$, $Na^+$ and $K^+$) were controlled. The improved piezoelectric properties were observed by addition of $LaFeO_3$ and control of A-site vacancies. In particular, a $d_{33}^*(S_{max}/E_{max})$ value of 614pm/V and an electric field induced strain of 0.33% was observed in $0.97Bi_{0.505}(Na_{0.78}K_{0.22})_{0.485}TiO_3-0.03LaFeO_3$ ceramic.

A-site Non-stoichiometric Effects of Bi0.5(Na0.78K0.22)0.5TiO3 Ceramics on the Dielectric and Electrical Properties (Bi0.5(Na0.78K0.22)0.5TiO3 세라믹스의 A-site 비화학양론이 유전 및 전기적 특성에 미치는 영향)

  • Park, Jung Soo;Lee, Ku Tak;Yun, Ji Sun;Cho, Jeong Ho;Jeong, Young Hun;Paik, Jong Hoo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.12
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    • pp.803-808
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    • 2014
  • $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics with an excess $Bi^{3+}$ and a deficiency of $Na^+$ and $K^+$ were synthesized by a conventional solid state reaction method. The structure and morphology of $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics were characterized by X-ray diffraction and field emission scanning electron microscopy. The electric polarization and mechanical strain induced by external electric field, and the temperature dependence of dielectric constant were investigated. These results demonstrated that an ergodic relaxor phase can be induced by controls of the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. A phase boundary between non-ergodic and ergodic relaxor phases can be observed at ambient temperature. The ergodic relaxor phase can be transferred to the ferroelectric phase by application of the electric field. The stability of the induced ferroelectric phases strongly depends on the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. The maximum strain of 0.31% was observed in $Bi_{0.51}(Na_{0.78}K_{0.22})_{0.47}TiO_3$ ceramics sintered at $1,150^{\circ}C$ for 2 h.

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.

Effect of LaFeO3 Doping on the Ferroelectric and Piezoelectric Properties of Bi0.5(Na0.78K0.22)0.5TiO3 Lead-Free Piezoceramics (LaFeO3 함량에 따른 (1-x)Bi0.5(Na0.78K0.22)0.5TiO3-xLaFeO3의 강유전, 압전 특성)

  • Park, Chun-Kil;Lim, Ji-Ho;Park, Jung-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.3
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    • pp.157-161
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    • 2017
  • $(1-x)Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3-xLaFeO_3$ ceramics were fabricated using a solid state reaction method. The microstructural, ferroelectric and piezoelectric properties were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), and polarization hysteresis loops (P-E). XRD results indicated that BNKT ceramic crystal structure modified by $LaFeO_3$ was transformed from a ferroelectric tetragonal to a non-polar pesudo-cubic phase with increased $LaFeO_3$ content. The improved piezoelectric properties resulted from the addition of $LaFeO_3$ up to 3 mol%. The $LaFeO_3$ 3mol% sample showed markedly improved piezoelectric and strain behaviors in comparison with pure BNKT ceramic.

Development of Bi0.5(Na0.78K0.22)0.5TiO3 Lead-free Piezoelectric Ceramic Material with Core-shell Structure for Biomedical (바이오 메디컬용 코어-쉘 구조의 Bi0.5(Na0.78K0.22)0.5TiO3계 무연압전세라믹 소재의 개발)

  • Seong-jun Yun;Joonsoo Bae
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.46 no.3
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    • pp.15-22
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    • 2023
  • BNKT Ceramics, one of the representative Pb free based piezoelectric ceramics, constitutes a perovskite(ABO3) structure. At this time, the perovskite structure (ABO3) is in the form where the corners of the octahedrons are connected, and in the unit cell, two ions, A and B, are cations, A ion is located at the body center, B ion is located at each corner, and an anion O is located at the center of each side. Since Bi, Na, and K sources constituting the A site are highly volatile at a sintering temperature of 1100℃ or higher, it is difficult to maintain uniformity of the composition. In order to solve this problem, there should be suppression of volatilization of the A site material or additional compensation of the volatilized. In this study, the basic composition of BNKT Ceramics was set to Bi0.5(Na0.78K0.22)0.5TiO3 (= BNKT), and volatile site (Bi, Na, and K sources) were coated in the form of a shell to compensate additionally for the A site ions. In addition, the physical and electrical properties of BNKT and its coated with shell additives(= @BNK) were compared and analyzed, respectively. As a result of analyzing the crystal structure through XRD, both BNKT(Core) and @BNK(Shell) had perovskite phases, and the crystallinity was almost similar. Although the Curie temperature of the two sintered bodies was almost the same (TC = 290 ~ 300 ℃), it was confirmed that the d33 (piezoelectric coefficient) and Pr (residual polarization) values were different. The experimental results indicated that the additional compensation for a shell additive causes the coarsening, resulting in a decrease in sintering density and Pr(remanent polarization). However, coating shell additives to compensate for A site ion is an effective way to suppress volatilization. Based on these experimental results, it would be the biggest advantage to develop an eco-friendly material (Lead-free) that replaced lead (Pb), which is harmful to the human body. This lead-free piezoelectric material can be applied to a biomedical device or products(ex. earphones (hearing aids), heart rate monitors, ultrasonic vibrators, etc.) and skin beauty improvement products (mask packs for whitening and wrinkle improvement).

Low Temperature Sintering of BNKT Lead-Free Piezoelectric Ceramics Using CuO-Coated Na0.5Bi4.5Ti4O15 Templates (산화구리가 피복된 Na0.5Bi4.5Ti4O15 틀입자를 이용한 BNKT 무연 압전 세라믹스의 저온소성 연구)

  • Jeong, Gwang-Hwi;Lee, Sang-Seop;Ahn, Chang Won;Han, Hyoung Su;Lee, Jae-Shin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.33 no.5
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    • pp.337-343
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    • 2020
  • This study investigated the low temperature sintering with various templates of Bi-based lead-free piezoelectric ceramics. The effects of using CuO-coated Na0.5Bi4.5Ti4O15 templates on the sintering behavior as well as the dielectric, ferroelectric, and piezoelectric properties of Bi1/2(Na0.78K0.22)1/2TiO3 (BNKT) ceramics have been examined. In comparison with the specimens sintered with the Na0.5Bi4.5Ti4O15 templates without CuO coating, those sintered with the CuO-coated Na0.5Bi4.5Ti4O15 templates showed larger template sizes as well as a larger electric field induced strain (Smax/Emax) of 422 pm/V after sintering at temperatures as low as 975℃. These results are promising for low-cost multilayer ceramic actuator applications.

The Study on the Improvement of Piezoelectric and Electrical Characteristics of Bi0.5(Na0.78K0.22)0.5TiO3 Ceramics Modified by the La-based ABO3 Pervskite Structure (La 기반의 ABO3 구조를 갖는 첨가물에 따른 Bi0.5(Na0.78K0.22)0.5TiO3의 압전 및 전기적인 특성 향상 연구)

  • Lee, Ku Tak;Park, Jung Soo;Yun, Ji Sun;Cho, Jeong Ho;Jeong, Young Hun;Paik, Jong Hoo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.11
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    • pp.707-711
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    • 2014
  • The $0.99Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3-0.01LaAlO_3$, $0.01LaMnO_3$ or $0.01LaFeO_3$ (0.99BNKT-0.01LA, 0.01LM or 0.01LF) ceramics were prepared by a conventional mixed mothod. The structure and morphology of the lead free ceramics were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy). XRD results indicated that the BNKT ceramics modified by LA, LM or LF induced a transition from a ferroelectric tetragonal to a non-polar pseudo-cubic phase, leading to decrease in the remnant polarization ($P_r$) and coercive field ($E_c$) in the P-E hysterisis loops. The effects of the BNKT ceramics modified by La-based $ABO_3$ pervskite structure on the electric-field induced strain were investigated, and the largest normalized unipolar strain ($S_{max}/E_{max}$) was found in BNKT-0.01LF ceramic.

The Study on the Phase Transition and Piezoelectric Properties of Bi0.5(Na0.78K0.22)0.5TiO3-LaMnO3 Lead-free Piezoelectric Ceramics

  • Lee, Ku Tak;Park, Jung Soo;Cho, Jeong Ho;Jeong, Young Hun;Paik, Jong Hoo;Yun, Ji Sun
    • Journal of the Korean Ceramic Society
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    • v.52 no.4
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    • pp.237-242
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    • 2015
  • $Bi_{0.5}(Na_{0.78}K_{0.22})_{0.5}TiO_3$ (BNKT) lead-free piezoelectric ceramics modified by $LaMnO_3$ (LM) were fabricated by conventional solid-state method. The crystal structure and the morphology of the lead free ceramics were analyzed by XRD (X-ray diffraction) and FE-SEM (Field Emission Scanning Electron Microscopy). The LM modified BNKT ceramics have a phase transition from ferroelectric tetragonal to non-polar pseudo-cubic. Despite decreases in the remnant polarization ($P_r$) and coercive field ($E_c$) in the P-E hysteresis loops, the electric-field induced strain properties were significantly enhanced by the LM modification. The highest value of $S_{max}/E_{max}=412pm/V$ at an applied electric field of 5 kV/mm was found in BNKT-0.01LM ceramic.

Tailoring Low-field Strain Properties of [0.97Bi1/2(Na0.78K0.22)1/2TiO3-0.03LaFeO3]-Bi1/2(Na0.82K0.18)1/2TiO3 Lead-Free Relaxor/Ferroelectric Composites (무연 완화형/정규 강유전체 복합소재 [0.97Bi1/2(Na0.78K0.22)1/2TiO3-0.03LaFeO3]-Bi1/2(Na0.82K0.18)1/2TiO3의 저전계 전계유기 변형 특성 연구)

  • Hong, Chang-Hyo;Kang, Jin-Kyu;Jo, Wook;Lee, Jae-Shin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.6
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    • pp.342-347
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    • 2016
  • We investigated the effect of $Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3$ (BNKT) modification on the ferroelectric and electric-field-induced strain (EFIS) properties of lead-free $0.97Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3-0.03LaFeO_3$ (BNKTLF) ceramics as a function of BNKT content (x= 0, 0.1, 0.2, 0.3, 0.5, and 1). BNKT-modified BNKTLF powders were synthesized using a conventional solid-state reaction method. As the BNKT content x increased from 0 to 1 the normalized electric-field-induced strain ($S_{max}/E_{max}$) was observed to increase at relatively low fields, i.e., below the poling field. Moreover, BNKTLF-30BNKT showed about 460 pm/V as low as at 3 kV/mm, which is a considerably high value among the lead-free systems reported so far. Consequently, it was confirmed that ceramic-ceramic composite, a mixture of an ergodic relaxor matrix and embedded ferroelectric seeds, is a salient way to make lead-free piezoelectrics practical with enhanced EFIS at low field as well as less hysterical.

Effects of High-Energy Ball Milling and Sintering Time on the Electric-Field-Induced Strain Properties of Lead-Free BNT-Based Ceramic Composites

  • Nga-Linh Vu;Nga-Linh Vu;Dae-Jun Heo;Thi Hinh Dinh;Chang Won Ahn;Chang Won Ahn;Hyoung-Su Han;Jae-Shin Lee
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.36 no.5
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    • pp.505-512
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    • 2023
  • This study investigated crystal structures, microstructures, and electric-field-induced strain (EFIS) properties of Bi-based lead-free ferroelectric/relaxor composites. Bi1/2Na0.82K0.18)1/2TiO3 (BNKT) as a ferroelectric material and 0.78Bi1/2(Na0.78K0.22)1/2TiO3-0.02LaFeO3 (BNKT2LF) as a relaxor material were synthesized using a conventional solid-state reaction method, and the resulting BNKT2LF powders were subjected to high-energy ball milling (HEBM) after calcination. As a result, HEBM proved a larger average grain size of sintered samples compared to conventional ball milling (CBM). In addition, the increased sintering time led to grain growth. Furthermore, HEBM treatment and sintering time demonstrated a significant effect on EFIS of BNKT/BNKT2LF composites. At 6 kV/mm, 0.35% of the maximum strain (Smax) was observed in the HEBM sample sintered for 12 h. The unipolar strain curves of CBM samples were almost linear, indicating almost no phase transitions, while HEBM samples displayed phase transitions at 5~6 kV/mm for all sintering time levels, showing the highest Smax/Emax value of 700 pm/V. These results indicated that HEBM treatment with a long sintering time might significantly enhance the electromechanical strain properties of BNT-based ceramics.