• Title/Summary/Keyword: Relaxor ferroelectrics

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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.

Ferroelectric Properties and DPT in the Perovskite PMT-PT System (Perovskite PMT-PT계의 강유전 특성 및 확산상전이)

  • Kim, Y.J.
    • Journal of the Korean Vacuum Society
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    • v.17 no.2
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    • pp.122-129
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    • 2008
  • Ferroelectric properties of the PMT-PT were also studied from the temperature dependence of hysteresis loops using a method slightly modified from Sawyer-Tower's. Dielectric, pyroelectric and piezoelectric properties of the ceramics in the system PMT-PT were investigated. The resulted densities of the PMT-PT ceramics system were greater than 97 % of the theoretical value. As observed SEM micrograph of the fracture surfaces of the PMT-PT ceramics system, the average grain sizes were increased about 3-5 ${\mu}m$ to 6-8 ${\mu}m$ with increasing sintering temperature. The specimens with PT<0.30 for PMT-PT solid solution system exhibited the dielectric and pyroelectric properties of a typical relaxor ferroelectrics. The composition with the maximum dielectric constant exhibits relatively superior pyroelectric and piezoelectric properties.

Dielectric and Ferroelectric Properties of Nb Doped BNT-Based Relaxor Ferroelectrics

  • Maqbool, Adnan;Hussain, Ali;Malik, Rizwan Ahmed;Zaman, Arif;Song, Tae Kwon;Kim, Won-Jeong;Kim, Myong-Ho
    • Korean Journal of Materials Research
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    • v.25 no.7
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    • pp.317-321
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    • 2015
  • The effects of Nb doping on the crystal structure, microstructure, and dielectric ferroelectric and piezoelectric properties of $(Bi_{0.5}Na_{0.5})_{0.935}Ba_{0.065}Ti_{(1-x)}Nb_xO_3-0.01SrZrO_3$ (BNBTNb-SZ, with ${\chi}=0$, 0.01 and 0.02) ceramics have been investigated. X-ray diffraction patterns revealed that all ceramics have a pure perovskite structure with tetragonal symmetry. The grain size of the ceramics slightly decreased and a change in grain morphology from square to spherical shape was observed in the Nb-doped samples. The maximum dielectric constant temperature ($T_m$) increases with increasing amount of Nb; however, ferroelectric-relaxor transition temperature ($T_{F-R}$) and maximum dielectric constant (${\varepsilon}_m$) values decrease gradually. Nb addition disrupted the polarization hysteresis loops of the BNBT-SZ ceramics by leading a reduction in the remnant polarization coercive field and piezoelectric constant.

Effect of $MnO_2$ Addition on the Electric Properties in Pb($Mg_{1/3}Nb_{2/3}$)$O_3$ Relaxor Ferroelectrics ($MnO_2$ 첨가에 따른 Pb($Mg_{1/3}Nb_{2/3}$)$O_3$계 완화형 강유전체에서의 전기적 물성변화)

  • 박재환
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.7
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    • pp.562-566
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    • 2001
  • The effects of MnO$_2$ addition on the properties in Pb(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ relaxor ferroelectrics were studied in the phase transition temperature range from -4$0^{\circ}C$ to 11$0^{\circ}C$. Specimens were made via solid state processing method. Dielectric properties, piezoelctric properties, electric-field-induced strain were examined to clarify the effect of MnO$_2$ addition in 0.9MN-0.1PT. As the amount of MnO$_2$ increases, the maximum dielectric constant and the dielectric loss decreases. Q$_{m}$ increased by increasing the doping contents of Mn. When 0.5wt% MnO$_2$ was doped, Q$_{m}$ increased from 95 to 480. The electric-filed-induced strain and polarization decreases as the amount of MnO$_2$ increases. From the experimental results, it was suggested that Mn behaves as an ferroelectric domain pinning element.ent.

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Phase Transformation and Dielectric Relaxation in $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ Relaxor Ferroelectrics (완화형 강유전체 $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$계에서의 상전이 및 Relaxation 거동)

  • Park, Jae-Hwan
    • Journal of the Korean Ceramic Society
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    • v.38 no.10
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    • pp.953-957
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    • 2001
  • To study various relaxation phenomena of $Pb(Mg_{1/3}Nb_{2/3})O_3$ relaxor ferroelectrics, weak electric-field properties as well as strong electric-field properties were investigated in the frequency range from 1 Hz to 100 kHz. The temperature dependence of the dielectric properties were measured under the low electric-field of 1 V/mm in the phase transition temperature range from $-40^{\circ}C$ to $90^{\circ}C$. The dielectric properties obtained from the slope of the dielectric hysteresis loop and the temperature dependence of the pyroelectric properties were also investigated. When fitting all the experimental data with the Vogel-Fulcher relation, experimental data were agreed with the equation closely. Thus, dielectric relaxations could be modeled by the Vogel-Fulcher relation not only for the low electric-field but also for the high electric-field.

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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.