Jianqiang Zhao

Publications (2)4.17 Total impact

• Article: Investigation of ferroelectric phase transition for modified barium titanate in multilayer ceramic capacitors by in situ Raman scattering and dielectric measurement

  Gang Yang, Zhenxing Yue, Tieyu Sun, Jianqiang Zhao, Zhengwen Yang, Longtu Li
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  ABSTRACT: The ferroelectric phase behaviors of modified BaTiO3 in X7R multilayer ceramic capacitors (MLCCs) were investigated by dielectric measurements and in situ Raman scattering. The in situ thermo-Raman scattering shows that because of a residual stress existing in the MLCCs, the tetragonal to cubic phase transition for modified BaTiO3 in MLCCs takes place over a wide temperature range of 373K to 473K, suggesting a diffuse-like characteristic which can be well explained by a modified phenomenological thermodynamic model, while the dielectric measurement indicates that the tetragonal to cubic transition occurs at 393K. A disagreement exists between the two experimental results. Furthermore, a dc field-induced paraelectric to ferroelectric transition was identified by the two measurement techniques, but their phase-transition mechanisms are different. The dielectric measurement reveals the polar-micro-region to macro-domain transformation in the shell part of the core–shell structure while the in situ Raman scattering shows the cubic to tetragonal transition under a dc bias field.
  Applied Physics A 05/2012; 91(1):119-125. · 1.63 Impact Factor
• Article: Dielectric behaviour of BaTiO3-based ceramic multilayer capacitors under high dc bias field

  Gang Yang, Zhenxing Yue, Jianqiang Zhao, Hai Wen, Xiaohui Wang, Longtu Li
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  ABSTRACT: The dielectric behaviour of X7R-MLCCs with different active layers under high dc bias field (up to 6.25 MV m−1) has been investigated in the whole measurement temperature range from 213 to 453 K. The results show that as the dc bias field increases, the dielectric permittivity in the whole measurement range and the frequency dispersion at lower temperature are both suppressed, while dielectric loss initially decreases till the temperature reaches about 423 K and subsequently remains invariable. These results are attributed to the response of the core-shell structure in grains to the applied dc bias field. Furthermore, the dielectric permittivity of X7R-MLCCs with more dielectric layers is more significantly affected because of a more powerful pinning effect of the residual stress between the dielectric layer and the Ni electrode on the migration of the domain walls and the influence of created interfaces on dielectric properties of the dielectric materials close to the interface. The Curie peaks for two samples shift towards higher temperature at a rate 0.55 × 10−5 K m V−1 in the presence of the dc bias field. It is more significant that an interesting field-induced transition from paraelectric phase to ferroelectric phase in the shell part was found at about 323 K and Curie temperature.
  Journal of Physics D Applied Physics 08/2006; 39(16):3702. · 2.54 Impact Factor