• Title, Summary, Keyword: Vogel-Fulcher law

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Relaxor Behaviors in xBaTiO3-(1-x)CoFe2O4 Materials

  • Dung, Cao Thi My;Thi, Nhu Hoa Tran;Ta, Kieu Hanh Thi;Tran, Vinh Cao;Nguyen, Bao Thu Le;Le, Van Hieu;Do, Phuong Anh;Dang, Anh Tuan;Ju, Heongkyu;Phan, Bach Thang
    • Journal of Magnetics
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    • v.20 no.4
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    • pp.353-359
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    • 2015
  • Dielectric properties of $xBaTiO_3-(1-x)CoFe_2O_4$ composite materials have been investigated. Dielectric properties of $BaTiO_3$, $CoFe_2O_4$ and $0.5BaTiO_3-0.5CoFe_2O_4$ samples show frequency dependence, which is classified as relaxor behavior with different relaxing degree. The relaxor behaviors were described using the modified Curier-Weiss and Vogel-Fulcher laws. Among three above samples, the $BaTiO_3$ sample has highest relaxing degree. Photoluminescence spectral indicated defects, which might in turn control relaxing degree.

Low-Temperature Characterization of Domain Wall Dynamics and Electrical Conduction in a Proton-Irradiated K(H0.21D0.79)2PO4 System

  • Lee, Cheol Eui;Oh, Byoung Hoo;Kim, Se-Hun
    • New Physics: Sae Mulli
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    • v.67 no.2
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    • pp.232-236
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    • 2017
  • We investigated the longitudinal electrical conductivity associated with the domain-wall dynamics in proton-irradiated $K(H_{0.21}D_{0.79})_2PO_4$ single crystals a temperatures below room temperature. Frequency-dependent longitudinal dielectric-loss measurements allowed us to investigate the changes in the domain-wall dynamics of the proton-irradiated crystal with a ferroelectric phase-transition temperature increase of 8 K. Using the Vogel-Fulcher function, we found that proton irradiation produced a slight increase in the activation energy of domain freezing. The temperature dependence of the power-law exponent n in frequency-dependent electrical conductivity in proton-conducting systems decreased at temperatures near the phase-transition temperature $T_{c2}$. In addition, the temperature dependence of the electrical conductivity shifted to higher temperatures because of the increased phase-transition temperature arising from the proton irradiation.