• Title/Summary/Keyword: Bismuth ferrite

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Phase Evolution Behavior of (Bi,Nd)(Fe,Ti)O3 Ceramics and Thin Films ((Bi,Nd)(Fe,Ti)O3 세라믹스와 박막의 상형성 거동)

  • Kim, Kyung-Man;Lee, Hee-Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.12
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    • pp.949-955
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    • 2010
  • Nd and Ti co-doped bismuth ferrite $(Bi_{1-x}Nd_x)(Fe_{1-y}Ti_y)O_3$ (x, y = 0, 0.05, 0.1, 0.2) ceramics and thin films were synthesized through the conventional mixed-oxide process and pulsed laser deposition (PLD), respectively. Nd and Ti co-doping effect was examined with emphasis on how these impurities affect phase formation behavior as there could be the improvement in leakage current problems often associated with multiferroic $BiFeO_3$ (BFO) thin films. The lattice constants of BFO ceramics decreased with Nd doping concentration up to 10mol%, while they further decreased with Nd and Ti co-doping to about 20%. BFO thin films obtained by the PLD process revealed random polycrystalline structure. Similar to bulk BFO ceramic, Nd and Ti co-doping effectively suppressed the formation of unwanted secondary phase and thus stabilized the perovskite phase in BFO thin films.

Magnetic and Electric Properties of Multiferroic Ni-doped BiFeO3

  • Yu, Yeong-Jun;Hwang, Ji-Seop;Park, Jeong-Su;Lee, Ju-Yeol;Gang, Ji-Hun;Kim, Gi-Won;Lee, Gwang-Hun;Lee, Bo-Hwa;Lee, Yeong-Baek
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.182-182
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    • 2014
  • Multiferroic materials have attracted much attention due to their own fascinating fundamental physical properties and potential technological applications to magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because the enhanced ferromagnetism was found by the Fe-site ion substitution with magnetic ions. The structural, the magnetic and the ferroelectric properties of polycrystalline $BiFe_{1-x}Ni_xO_3$ (x=0, 0.01, 0.02, 0.03 and 0.05), which were prepared by the solid-state reaction and the rapid-sintering method, have been investigated. The x-ray diffraction patterns reveal that all the samples are in single phase and show rhombohedral structure with R3c space group. The magnetic properties are enhanced according to the doping content. The Ni-doped $BiFeO_3$ samples exhibit lossy P-E loop due to the oxygen vacancy. The leakage current density of Ni-doped samples (x=0.01 and 0.02) is increased by four orders of magnitude. On the other hand, the x=0.03 and 0.05 samples show the relative reduction of the leakage current.

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BiFeO3-based Lead-free Piezoelectric Ceramics (비스무스 페라이트계 무연 압전 세라믹스)

  • Choi, Jin-Hong;Kim, Hyun-Ah;Han, Seung-Ho;Kang, Hyung-Won;Lee, Hyeung-Gyu;Kim, Jeong-Seog;Cheon, Chae-Il
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.9
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    • pp.692-701
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    • 2012
  • Recently, many lead-free piezoelectric materials have been investigated for the replacement of existing Pb-based piezoelectric ceramics because of globally increasing environmental interest. There has been remarkable improvement in piezoelectric properties of some lead-free ceramics such as $(Bi,Na)TiO_3-(Bi,K)TiO_3-BaTiO_3$, $(Na,K)NbO_3-LiSbO_3$, and so on. However, no one still has comparable piezoelectric properties to lead-based materials. Therefore, new lead-free piezoelectric ceramics are required. $BiFeO_3$ has a rhombohedrally distorted perovskite structure at room temperature and a very high Curie temperature ($T_C$= 1,100 K). And a very large electric polarization of 50 ~ 60 ${\mu}C/cm^2$ has been reported both in epitaxial thin film and single crystal $BiFeO_3$. Therefore, a high piezoelectric effect is expected also in a $BiFeO_3$ ceramics. The recent research activities on $BiFeO_3$ or $BiFeO_3$-based solid solutions are reviewed in this article.

Crystal Structure and Microstructure Variation of Nonstoichiometric Bi1±xFeO3±δ and Ti-doped BiFeO3 Ceramics under Various Sintering Conditions (비화학양론적 Bi1±xFeO3±δ와 Ti가 첨가된 BiFeO3의 소결조건에 따른 결정구조와 미세구조 변화)

  • Bae, Jihee;Kim, Jun Chan;Kim, Myong-Ho;Lee, Soonil
    • Korean Journal of Materials Research
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    • v.30 no.2
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    • pp.61-67
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    • 2020
  • BiFeO3 with perovskite structure is a well-known material that has both ferroelectric and antiferromagnetic properties called multiferroics. However, leaky electrical properties and difficulty of controlling stoichiometry due to Bi volatility and difficulty of obtaining high relative density due to high dependency on the ceramic process are issues for BiFeO3 applications. In this work we investigated the sintering behavior of samples with different stoichiometries and sintering conditions. To understand the optimum sintering conditions, nonstoichiometric Bi1±xFeO3±δ ceramics and Ti-doped Bi1.03Fe1-4x/3TixO3 ceramics were synthesized by a conventional solid-state route. Dense single phase BiFeO3 ceramics were successfully fabricated using a two-step sintering and quenching process. The effects of Bi volatility on microstructure were determined by Bi-excess and Ti doping. Bi-excess increased grain size, and Ti doping increased sintering temperature and decreased grain size. It should be noted that Ti-doping suppressed Bi volatility and stabilized the BiFeO3 phase.

Enhanced Piezoelectric Properties of (1-x)[0.675BiFeO3-0.325BaTiO3]-xLiTaO3 Ternary System by Air-Quenching

  • Akram, Fazli;Malik, Rizwan Ahmed;Lee, Soonil;Pasha, Riffat Asim;Kim, Myong Ho
    • Korean Journal of Materials Research
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    • v.28 no.9
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    • pp.489-494
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    • 2018
  • Lead free $(1-x)(0.675BiFeO_3-0.325BaTiO_3)-xLiTaO_3$ (BFBTLT, x = 0, 0.01, 0.02, and 0.03, with 0.6 mol% $MnO_2$ and 0.4 mol% CuO) were prepared by a solid state reaction method, followed by air quenching and their crystalline phase, morphology, dielectric, ferroelectric and piezoelectric properties were explored. An X-ray diffraction study indicates that lithium (Li) and tantalum (Ta) were fully incorporated in the BFBT materials with the absence of any secondary phases. Dense ceramic samples (> 92 %) with a wide range of grain sizes from $3.70{\mu}m$ to $1.82{\mu}m$ were obtained in the selected compositions ($0{\leq}x{\leq}0.03$) of BFBTLT system. The maximum temperatures ($T_{max}$) were mostly higher than $420^{\circ}C$ in the studied composition range. The maximum values of maximum polarization ($P_{max}{\approx}31.01{\mu}C/cm^2$), remnant polarization ($P_{rem}{\approx}22.82{\mu}C/cm^2$) and static piezoelectric constant ($d_{33}{\approx}145pC/N$) were obtained at BFBT-0.01LT composition with 0.6 mol% $MnO_2$ and 0.4 mol% CuO. This study demonstrates that the high $T_{max}$ and $d_{33}$ for BFBTLT ceramics are favorable for industrial applications.

Enhanced Sintering Behavior and Electrical Properties of Single Phase BiFeO3 Prepared by Attrition Milling and Conventional Sintering

  • Jeon, Nari;Moon, Kyoung-Seok;Rout, Dibyranjan;Kang, Suk-Joong L.
    • Journal of the Korean Ceramic Society
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    • v.49 no.6
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    • pp.485-492
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    • 2012
  • Dense and single phase $BiFeO_3$ (BFO) ceramics were prepared using attrition milled calcined (coarse) powders of an average particle size of ${\approx}3{\mu}m$ by conventional sintering process. A relative density of ${\approx}96%$ with average grain size $7.3{\mu}m$ was obtained when the powder compacts were sintered at $850^{\circ}C$ even for a shorter duration of 10 min. In contrast, densification barely occurred at $800^{\circ}C$ for up to 12 h rather the microstruce showed the growth of abnormal grains. The grain growth behavior at different temperatures is discussed in terms of nonlinear growth rates with respect to the driving force. The sample sintered at $850^{\circ}C$ for 12 h showed enhanced electrical properties with leakage current density of $4{\times}10^{-7}A/cm^2$ at 1 kV/cm, remnant polarization $2P_r$ of $8{\mu}C/cm^2$ at 20 kV/cm, and minimal dissipation factor (tan ${\delta}$) of ~0.025 at $10^6$ Hz. These values are comparable to the previously reported values obtained using unconventional sintering techniques such as spark plasma sintering and rapid liquid phase sintering.