• Title/Summary/Keyword: Relaxor

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Direct Determination of Cationic Disordering in Sodium Bismuth Titanate

  • Choi, Si-Young;Ikuhara, Yuichi
    • Applied Microscopy
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    • v.42 no.3
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    • pp.164-173
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    • 2012
  • The relaxor ferroelectric feature in lead-free perovskite oxides, where the dipoles are randomly oriented and they can be feasibly aligned parallel to the external bias, is attracting lots of attention in the field of piezoelectric materials science, since it is one of candidates to replace the toxic lead-based materials that are still being commercially used. However, the origin of relaxor characteristic and its related atomic structure are still ambiguous. In this study, $Na_{1/2}Bi_{1/2}TiO_3$, chosen as a model relaxor system, was found to exhibit a cationic-disordered atomic structure; and furthermore the nonpolar atomic structure and its related oxygen tilting were ascertained via annular bright field imaging skill. We also found that this cationic disordering gives rise to the local formation of atomic vacancies.

Micro-Macro Domain Switching and Thermoelastic Martensitic Transformation in $PbZrO_3$-doped $Pb(Ni_{1/3}Nb_{2/3})O_3-PbTiO_3$ System ($PbZrO_3$가 첨가된 $Pb(Ni_{1/3}Nb_{2/3})O_3-PbTiO_3$ 계의 미소-거시 분역 반전과 열탄성 마르텐사이트 변태)

  • 윤만순;장현명
    • Journal of the Korean Ceramic Society
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    • v.32 no.9
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    • pp.967-976
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    • 1995
  • The possiblity of the existence of a spontaneous relaxor-normal ferroelectric transition was proposed and examined using 1~5 mol% PbZrO3-doped Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) systems having tetragonal symmetry at rom temperature. On cooling, the system with 60mol% Pb(Ni1/3Nb2/3)O3 underwent a spontaneous transition from a relaxor to a normal ferroelectric state. A microscopic examination demonstrates that the relaxornormal ferroelectric transition corresponds to a micro-macro domain switching accompanied with thermoelastic martensitic transformation. The long-range macrodomains below the transition temperature were characterized by twinlike 90$^{\circ}$macrodomains with tetragonal symmetry. The relaxor-normal ferroelectric transition was further correlated with the rhombohedral-tetragonal first-order structural transition.

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Sr/Ba Ratio Dependence of Dielectric Characteristics in Strontium Barium NiobateCeramics (Sr/Ba 비에 따른 Strontium Barium Niobate 세라믹스의 유전특성)

  • 김명섭;이준형;김정주;이희영;조상희
    • Journal of the Korean Ceramic Society
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    • v.38 no.12
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    • pp.1167-1173
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    • 2001
  • The tetragonal tungsten bronze type of Sr$_{x}Ba_{1-x}Nb_{2}O_{6}$(SBN) (0.3$\le$x$\ge$0.7) ceramics was synthesized by the solid state reaction method, and the dielectric properties of SBN ceramics as a function of Sr/Ba ratio were examined. With increasing Sr/Ba ratio in SBN ceramics, the Curie temperature decreased and the maximum dielectric constant at the Curie temperature increased. The relaxor behavior of the SBN ceramics as a function of Sr/Ba ratio was quantitatively evaluated. More relaxor behavior of dielectric characteristics was observed as the ratio of Sr/Ba increased. The experimental results are explained with a viewpoint of crystallography of tungsten bronze structured SBN ceramics.

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Effect of Poling Electric Field and Temperature Change on the Dielectric Anomalies of Relaxor Ferroelectric Strontium-Barium-Niobate Single Crystals

  • Shabbir, Ghulam;Ko, Jae-Hyeon;Kojima, Seiji
    • Journal of the Korean Physical Society
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    • v.73 no.10
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    • pp.1561-1565
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    • 2018
  • The dielectric properties of the uniaxial relaxor ferroelectric $Sr_xBa_{1-x}Nb_2O_6$ with x = 0.75 were investigated along the polar [001] direction as a function of temperature. The capacitance maximum showed the frequency dispersion commonly observed in relaxors. Additional weak dielectric anomalies were observed in the paraelectric phase; they were only seen during the heating process and disappeared upon subsequent cooling. These were attributed to the existence of large polar clusters strongly pinned at defects and/or to random fields and their metastable characters. Aligning the ferroelectric domains along the polar axis at room temperature removed the high-temperature dielectric anomalies. The dependences of the capacitance and the dielectric maximum temperature on the magnitude of the poling field were investigated.

Electric-Field-Induced Lattice Distortion and Related Properties in Relaxor Ferroelectrics (완화형 가유전체에서 전계인가에 따른 격자왜곡과 강유전물성의 상관관계)

  • 박재환;박재관;김윤호
    • Korean Journal of Crystallography
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    • v.12 no.1
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    • pp.14-19
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    • 2001
  • Effects of electric-field-induced lattice distortion on the polarization and strain were investigated in Pb(Mg/sub 1/3/Nb/sub 2/3)O₃ relaxor ferroelectric ceramics in the temperature range of -50℃∼90℃. The ratio of residual strain and polarization (S/sub r//P/sub r/ rarely depends on the temperature. However, the ratio of the electric field included strain and polarization (S/sub induced//P/sub induced/) increased as the temperature decreases below phase transition temperature. To explain these experimental results, a simple rigid ion model concentrating on only Bo/sub 6/ octahedron was suggested.

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Phase Transition and Relaxor Behaviors in the Lead Magnesium Niobate-based Ferroelectrics (Pb(Mg1/3Nb2/3)O3-based 강유전체의 상전이 및 완화특성)

  • Kim, Y.J.;Lee, J.H.
    • Journal of the Korean Vacuum Society
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    • v.17 no.2
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    • pp.148-155
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    • 2008
  • Dielectric and pyroelectric properties of relaxor ferroelectric in the PMN-PT solid solution series have been investigated. Features of the diffuse phase transition in PMN-PT system, typical relaxor ferroelectric materials, were studied as a function of temperature and frequency. The transition temperature of the ceramics with PT$\sim$0.325 did not depend on the measuring frequency. This can best realized in a relatively random environment that apparently is provided by PMN-rich complex perovskites, including those containing Pb. The composition with PT>0.35 show the characteristics of a normal single phase ferroelectric material. Thus the studies revealed that the morphotropic phase boundary in the PMN-PT system is in the vicinity of PT$\sim$0.3 and it has a small curvature and as a result the compositions near the morphotropic phase boundary show two phase transitions, rhombohedral$\rightarrow$tetragonal$\rightarrow$cubic, when the samples are heated up to higher temperature. The best optimum compositions are observed near the morphotropic phase boundary.

Phase Transition Behaviors of Lead-Free Piezoelectric (Na1/2Bi1/2TiO3)(1-x)-(BaTiO3)x (납이 포함되지 않은 압전 특성의 (Na1/2Bi1/2TiO3)(1-x)-(BaTiO3)x 상전이 거동 연구)

  • Lee, Byoungwan;Luo, Haosu;Kim, Jung Kyu
    • Ceramist
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    • v.23 no.1
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    • pp.101-109
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    • 2020
  • In this study, the phase transition behaviors of lead-free (Na1/2Bi1/2TiO3)(1-x)-(BaTiO3)x (NBT-BT) are investigated by using Brillouin spectroscopy. The elastic properties, sound velocity and absorption coefficient of NBT-BT are characterized as a function of temperature along different crystallographic axes. The temperature dependences of the elastic constants of NBT-BT near the morphotropic phase boundary are determined for the first time. The unpoled NBT-BT single crystals exhibits the typical relaxor behaviors, presenting broad acoustic and dielectric anomalies. The application of electric field induced discontinuous changes in the elastic properties at ~110℃, which indicates field-induced phase transition occurred. The electric field also changes the dielectric constant from more relaxor-like to ferroelectric-like dielectric behavior.

Improved Temperature Stability in Dielectric Properties of 0.8BaTiO3-(0.2-x)NaNbO3-xBi(Mg1/2Ti1/2)O3 Relaxors

  • Goh, Yumin;Kim, Baek-Hyun;Bae, Hyunjeong;Kwon, Do-Kyun
    • Journal of the Korean Ceramic Society
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    • v.53 no.2
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    • pp.178-183
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    • 2016
  • Ferroelectric relaxor ceramics with $BaTiO_3-NaNbO_3-Bi(Mg_{1/2}Ti_{1/2})O_3$ ternary compositions (BT-NN-BMT) have been prepared by sol-gel powder synthesis and consequent bulk ceramic processing. Through the modified chemical approach, fine and single-phase complex perovskite compositions were successfully obtained. Temperature and frequency dependent dielectric properties indicated typical relaxor characteristics of the BT-NN-BMT compositions. The ferroelectric-paraelectric phase transition became diffusive when NN and BMT were added to form BT based solid solutions. BMT additions to the BT-NN solid solutions affected the high temperature dielectric properties, which might be attributable to the compositional inhomogeneity of the complex perovskite and resulting weak dielectric coupling of the Bi-containing polar nanoregions (PNRs). The temperature stability of the dielectric properties was good enough to satisfy the X9R specification. The quasi-linear P-E response and the temperature- stable dielectric properties imply the high potential of this ceramic compound for use in high temperature capacitors.

Preparation and Field-Induced Electrical Properties of Perovskite Relaxor Ferroelectrics

  • Fan, Huiqing;Peng, Biaolin;Zhang, Qi
    • Transactions on Electrical and Electronic Materials
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    • v.16 no.1
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    • pp.1-4
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    • 2015
  • (111)-oriented and random oriented $Pb_{0.8}Ba_{0.2}ZrO_3$ (PBZ) perovskite relaxor ferroelectric thin films were fabricated on Pt(111)/$TiO_x$/$SiO_2$/Si substrate by sol-gel method. Nano-scaled antiferroelectric and ferroelectric two-phase coexisted in both (111)-oriented and random oriented PBZ thin film. High dielectric tunability (${\eta}=75%$, E = 560 kV/cm) and figure-of-merit (FOM ~ 236) at room temperature was obtained in (111)-oriented thin film. Meanwhile, giant electrocaloric effect (ECE) (${\Delta}T=45.3K$ and ${\Delta}S=46.9JK^{-1}kg^{-1}$ at $598kVcm^{-1}$) at room temperature (290 K), rather than at its Curie temperature (408 K), was observed in random oriented $Pb_{0.8}Ba_{0.2}ZrO_3$ (PBZ) thin film, which makes it a promising material for the application to cooling systems near room temperature. The giant ECE as well as high dielectric tunability are attributed to the coexistence of AFE and FE phases and field-induced nano-scaled AFE to FE phase transition.