T. K. Song

Changwon National University, Changnyeong, South Gyeongsang, South Korea

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Publications (195)259.02 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Lead-free piezoelectric (0.96B0.5N0.5TiO3)-0.04BaZrO3 (BNT-BZ4) was synthesized by using a solid-state reaction method. SEM micrograph shows dense microstructure. X-ray diffraction (XRD) indicated the formation of a BNB-BZ4 single phase having pseudocubic symmetry. A maximum value of remnant polarization (30μC/cm2) and piezoelectric constant (112 pC/N) was observed for BNT-BZ4 ceramic. The temperature dependences of the dielectric properties of BNT-BZ4 were investigated in the temperature range of 25-600°C at various frequencies (0.1 Hz-1 MHz). The maximum dielectric constant value (r) reaches a highest value of 4046 (at 10 kHz). The electrical properties were investigated by using complex impedance spectroscopy and provided better understanding of relaxation process.
    IOP Conference Series Materials Science and Engineering 06/2014; 60(1):012043.
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    ABSTRACT: Ferroelectrics Publication details, including instructions for authors and subscription information: makes every effort to ensure the accuracy of all the information (the "Content") contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
    Ferroelectrics 05/2014; 4641:107-115893159. · 0.42 Impact Factor
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    ABSTRACT: Ferroelectrics Publication details, including instructions for authors and subscription information: makes every effort to ensure the accuracy of all the information (the "Content") contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
  • [Show abstract] [Hide abstract]
    ABSTRACT: Flexoelectric control of defect formation and associated electronic function is demonstrated in ferroelectric BiFeO3 thin films. An intriguing, so far never demonstrated, effect of internal electric field (Eint ) on defect formation is explored by a means of flexoelectricity. Our study provides novel insight into defect engineering, as well as allows a pathway to design defect configuration and associated electronic function.
    Advanced Materials 05/2014; · 14.83 Impact Factor
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    ABSTRACT: Polycrystalline, sodium excess Ta-modified (K0.470Na0.545)(Nb0.55Ta0.45)O3 ceramics were synthesized by reactive templated grain growth method. The crystal structure and microstructure of the synthesized (K0.470Na0.545)(Nb0.55Ta0.45)O3 ceramics were examined with X-ray diffraction and scanning electron microscopy. Complex impedance spectroscopy measurements have been carried out to investigate electrical properties in wide frequency range (0.1 Hz – 1 MHz) at different temperatures. Contributions from grain boundaries and from the grain interiors can be distinguished in the complex impedance plots. Moreover, (K0.470Na0.545)(Nb0.55Ta0.45)O3 ceramics were found to exhibit negative temperature coefficient of resistance.
    Ferroelectrics 05/2014; 4641:107-115893159. · 0.42 Impact Factor
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    ABSTRACT: The crystal structure, electric field-induced strain (EFIS) and piezoelectric properties of lead-free SrZrO 3 -modified Bi 0.5 Na 0.5 TiO 3 – 0.065BaTiO 3 (BNBT–SZ100x, with x ¼0–10) ceramics were investigated. The X-ray diffraction analysis revealed a phase transformation from tetragonal to pseudocubic symmetry with increasing amounts of SZ. A large EFIS of 0.39% was obtained at the critical composition of BNBT– SZ2 which corresponds to a normalized strain (S max /E max) of 722 pm/V at a low applied field of $5.5 kV/mm. Ferroelectric curves indicated a disruption of ferroelectric order and a decrease in the remnant polarization and coercive field. A maximum value of piezoelectric constant (197 pC/N) and electromechanical coupling coefficient (29.4%) was obtained for SZ1 ceramics. The maximum dielectric constant temperature (T m) and depolarization temperature (T d) shifted towards lower temperatures and curves became more diffuse with increasing amounts of SZ. The results indicate that BNBT–SZ100x ceramics can be promising candidates for lead-free actuators.
    Ceramics International 04/2014; · 1.79 Impact Factor
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    ABSTRACT: Na-excess (Na0.53+xK0.47)(Nb0.55Ta0.45)O3 ceramics (x = 0.0, 0.005, 0.01, 0.015, 0.02, and 0.03) were prepared through the solid-state reaction method. The effects of Na excess and Ta substitution on dielectric behaviors and piezoelectric properties were investigated. Crystallized single phases were confirmed using X-ray diffraction. In particular, the orthorhombic–tetragonal polymorphic phase-transition temperature (TO–T) was observed near room temperature, and the piezoelectric properties were enhanced, even for small Na excesses and Ta substitution. The optimized piezoelectric coefficient d33 and planar electromechanical coupling coefficient kp were estimated to be 320–340 pC/N and 0.36, respectively.
    Physica Status Solidi (A) Applications and Materials 04/2014; · 1.46 Impact Factor
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    ABSTRACT: The effect of BaZrO 3 (BZ) addition on the crystal structure, ferroelectric, and piezoelectric properties of Na 0.5 Bi 0.5 TiO 3 (NBT) ceramics synthesized by a conventional solid-state reaction method was systemically investigated. The X-ray diffraction profile reveals the formation of single-phase perovskite structure for all BZ modified NBT ceramics in composition range (x ¼ 0–0.08). With the increase in BZ content, the maximum dielectric constant (T m) and depolariza-tion temperature (T d) peaks shift towards lower temperatures. At room temperature, the ferroelectric response increase with increase in BZ concentration. A maximum value of remanent polarization (P r) 30 mC/cm 2 was obtained at x ¼ 0.04 and, however, with further increase in BZ content polarizations values decrease. The piezoelectric constant (d 33) increased from 60 pC/N for pure NBT to 112 pC/N for x ¼ 0.040. Furthermore, a significant enhancement in the normalized strain (d à 33 ¼ S max / E max ¼ 500 pm/V) was observed at x ¼ 0.055 which can be attributed to ferroelectric and relaxor ferroelectric phase transformation. ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Perovskite type materials with gener-al formula ABO 3 have been attracted much research interest for the past several decades because of their interesting crystal structure symmetry, excellent piezoelectric, ferro-electric, dielectric properties, and wide range of industrial applications [1, 2]. Among these materials, the A-site disordered perovskites; (A
    Physica Status Solidi (A) Applications and Materials 01/2014; · 1.46 Impact Factor
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    ABSTRACT: NaNbO3 particles were synthesized via three different techniques: molten salt synthesis (MSS), conventional mixed-oxide route, and topochemical microcrystal conversion. X-ray diffraction reveals that NaNbO3 particles produced via MSS as well as mixed-oxide route have similar crystal symmetry, however, is different from the topochemical microcrystal conversion method. Field emission electron microscopy shows that NaNbO3 particles produced via three different techniques have different grain sizes and morphologies. Furthermore, their Raman spectral lines show different structural types for different methods. High dielectric constant and high Currie temperature were realized in NaNbO3 particles synthesized by mixed-oxide route as compared with MSS and topochemical microcrystal conversion methods.
    Materials and Manufacturing Processes 01/2014; 29(6). · 1.30 Impact Factor
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    Journal of Alloys and Compounds 01/2014; 593:97–102. · 2.39 Impact Factor
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    ABSTRACT: Lead-free piezoelectric ceramics (1 − x)Bi0.5Na0.5TiO3–xBaZrO3 (BNT–BZ100x, with x = 0–0.10) were prepared using a conventional solid-state reaction method. The crystal structure, microstructure, dielectric, ferroelectric, and piezoelectric properties of BNT–BZ100x ceramics were studied as functions of different BZ content. X-ray diffraction patterns revealed that the BZ completely diffused in the BNT lattice in the studied composition range. An appropriate amount of BZ addition improved the dielectric, ferroelectric, and piezoelectric properties of BNT ceramics. The remanent polarization (Pr) and piezoelectric constant (d33) increased from 22 μC/cm2 and 60 pC/N for pure BNT to 30 μC/cm2 and 112 pC/N for x = 0.040, respectively. In addition, electric field-induced strain was enhanced to its maximum value (Smax = 0.40%) with normalized strain (d*33 = Smax/Emax = 500 pm/V) at an applied electric field of 8 kV/mm for x = 0.055. The enhanced strain can be attributed to the coexistence of ferroelectric and relaxor ferroelectric phases.
    Current Applied Physics 01/2014; 14(3):331–336. · 1.81 Impact Factor
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    ABSTRACT: Lead-free polycrystalline (K0.48Na0.52)1+x (Nb0.55Ta0.45)O3 (x = 0, 0.01, 0.02 and 0.03) thin films have been grown on Pt(111)/Ti/SiO2/Si substrates using KrF excimer laser ablation to investigate the effects of A-site ion excess. The film at x = 0.01 exhibited good ferroelectric hysteresis loop with a remnant polarization 2P r of 30 μC/cm2 and coercive field 2E c of 61 kV/cm. The piezoelectric coefficient d 33,f of the KNNT film with x = 0.01 was found to amount to 79 pm/V. These improved ferroelectric and piezoelectric properties were attributed to the excess of A-site Na and K ions.
    Ferroelectrics 01/2014; 465(1). · 0.42 Impact Factor
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    ABSTRACT: Pure Bi6Fe2Ti3O18 and vanadium (V) doped Bi6Fe2Ti3O18 (Bi5.99Fe2Ti2.75V0.03O18) thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by a chemical solution deposition method. The Bi5.99Fe2Ti2.75V0.03O18 thin film exhibited improved electrical and multiferroic properties, such as leakage current densities, dielectric properties, ferroelectric and ferromagnetic properties. We consider that the improved properties might be related to the reduced concentration of oxygen vacancies and the decreased mobility of oxygen vacancies by V doping.
    Ferroelectrics 01/2014; 465(1). · 0.42 Impact Factor
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    ABSTRACT: Lead-free non-stoichiometric (K0.470Na0.545)(Nb0.55Ta0.45)O3 (KNNT) textured ceramics were prepared by a reactive templated grain growth method using NaNbO3 (NN) templates. The Plate-like NaNbO3 (NN) templates were synthesized from bismuth layer-structured Bi2.5Na3.5Nb5O18 (BNN) particles by a topochemical microcrystal conversion (TMC) method. Using 5 wt% of NN templates, textured KNNT ceramics were fabricated, and their crystal structure, microstructure, dielectric and piezoelectric properties were compared with non-textured KNNT ceramics prepared by a conventional solid state reaction method. The textured KNNT ceramics exhibited high grain orientation and high dielectric constant. In addition, piezoelectric properties of textured KNNT ceramics were improved, giving a high piezoelectric coefficient d33 = 390 pC/N and piezoelectric coupling coefficient kp = 0.60.
    Current Applied Physics 08/2013; 13(6):1055–1059. · 1.81 Impact Factor
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    ABSTRACT: Flexoelectricity can play an important role in the reversal of the self-polarization direction in epitaxial BiFeO3 thin films. The flexoelectric and interfacial effects compete with each other to determine the self-polarization state. In Region I, the self-polarization is downward because the interfacial effect is more dominant than the flexoelectric effect. In Region II, the self-polarization is upward, because the flexoelectric effect becomes more dominant than the interfacial effect.
    Advanced Materials 07/2013; · 14.83 Impact Factor
  • S. Kim, W. Kim, M. Lee, T. Song, D. Do
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    ABSTRACT: A 40% Mn-substituted BiFeO3 (BFMO) thin film was deposited on a Pt(111)/Ti/SiO2/Si(100) substrate by using a pulsed laser deposition method. The coexistence of rhombohedral and orthorhombic structures in the BFMO thin film was confirmed by using X-ray diffraction and Raman spectra investigation. The leakage current density of the BFMO thin film was larger than that of a pure polycrystalline BiFeO3 (BFO) thin film. In order to understand the leakage current behaviors, was investigated the leakage current mechanisms. The leakage current mechanism of the BFO thin film was found to be space-charge-limited conduction (SCLC), followed by trap-filled conduction causal by the increasing electric field strength. On the other hand, trap-filled conduction was not observed in the BFMO thin film. A leaky ferroelectric hysteresis loop was observed in the BFMO thin film, but not in the BFO thin film.
    Journal- Korean Physical Society 01/2013; 63(12). · 0.51 Impact Factor
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    ABSTRACT: Effects of heat-treat procedure and sintering temperatures were investigated in 0.67Bi1.05FeO3-0.33BaTiO3ceramics. The structure, dielectric, ferroelectric, and piezoelectric properties of ceramics made by normal cooling or quenched cooling process were investigated. All ceramics show single pseudo-cubic perovskite crystal structure. Although the structure was not changed but other properties were much changed by heat-treatment. The normally cooled ceramic showed ‘pinched’ ferroelectric hysteresis loops with remanent polarization value of about 10 μC/cm2. On the contrary, the quenched ceramic showed ‘normal’ ferroelectric hysteresis loops with remanent polarization value of about 17 μC/cm2. The piezoelectric constant d 33value of 13 pC/N in normally cooled ceramic was improved to 39 pC/N in quenched ceramic. These improved results were attributed to the reduced populations of defects made during the heat-treatments.
    Ferroelectrics 01/2013; 452(1). · 0.42 Impact Factor
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    ABSTRACT: A phenomenological approach to explain the change of phase transition temperatures (T C) of Pb(Zr,Ti)O3-BiFeO3 (PZT-BF) mixed system was proposed. By introducing coupling terms independent of composition together with the averaged free energy terms, the change of T C was well explained in PbTiO3-BiFeO3 (PT-BF) mixed system. From the parameters obtained from PT-BF system of a 1 and a 11 in Landau-Devonshire theory, we could explain the change of T C in PZT-BF system in tetragonal phase.
    Ferroelectrics 01/2013; 450(1). · 0.42 Impact Factor
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    ABSTRACT: In this study, trivalent element doped SnO2 thin films were deposited on glass substrate using pulsed laser deposition method. The effect of trivalent elements (Al2O3, Bi2O3, Sb2O3 and Y2O3) doping on the structural, electrical and optical properties have been studied using X-ray diffraction (XRD), photoluminescence and resistivity measurements. XRD results indicated that all films exhibited single phase nature with (101) preferred orientation. Among all the films, the 6 wt% Sb doped film had the lowest value of the resistivity. Photoluminescence study inferred that all the films showed violet–blue emission and the intensity of this emission decrease with the increase in the doping content.
    Current Applied Physics 12/2012; 12:S21–S24. · 1.81 Impact Factor
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    ABSTRACT: The structural, electrical, and multiferroic properties of the double-layered (Bi0.95La0.05)(Fe0.97Cr0.03)O3/NiFe2O4 thin film deposited on a Pt(111)/Ti/SiO2/Si(100) substrate by a chemical solution deposition method are reported. The formation of the perovskite-based distorted rhombohedral and spinel phases was confirmed by X-ray diffraction analysis and Raman spectroscopy. The surface morphology and film thickness were analyzed by field emission scanning electron microscopy. The low leakage current density (5.83× 10-7 A/cm2 at 100 kV/cm) was measured from the double-layered thin film. Potential multiferroic properties, such as a well-saturated ferroelectric hysteresis loop with large 2 Pr (61 μC/cm2) and 2 Ec (652 kV/cm) (at an applied electric field of 952 kV/cm), and a ferromagnetic hysteresis loop having 2 Mr (18.6 emu/cm3) with 2 Hc (0.943 kOe) (at an applied magnetic field of 20 kOe), were observed from the double-layered thin film.
    Japanese Journal of Applied Physics 09/2012; 51(9). · 1.07 Impact Factor

Publication Stats

570 Citations
259.02 Total Impact Points

Institutions

  • 2001–2014
    • Changwon National University
      • • Department of Physics
      • • Department of Ceramic Science and Engineering
      Changnyeong, South Gyeongsang, South Korea
  • 2012
    • CHA University
      • Department of Obstetrics and Gynecology
      Sŏul, Seoul, South Korea
  • 2010
    • Samsung Medical Center
      • Department of Obstetrics and Gynecology
      Sŏul, Seoul, South Korea
  • 1994–2008
    • Seoul National University
      • Department of Physics and Astronomy
      Seoul, Seoul, South Korea
  • 1997–1998
    • Korea Institute of Science and Technology
      Sŏul, Seoul, South Korea