Relaxational polarization in polar dielectric barium magnesium niobate
نویسندگان
چکیده
Relaxor-like dielectric behavior, analogous to that found in lead magnesium niobate, has been induced in the polar dielectric barium magnesium niobate ~BMN!. In BMN, the dielectric constant was increased and the temperature of the maximum dielectric constant was shifted to a lower temperature with a decrease in measurement frequency with increasing A-site vacancy concentrations. The frequency dispersion of the permittivity maximum exhibited good agreement with the Arrhenius relationship. An activation energy of 0.15 eV and a preexponential factor 10 s were determined. No frequency dispersion in the imaginary part of the permittivity was found below the temperature of the dielectric maximum. A linear polarization-electric field dependence was observed at room temperature. A polarization of 0.3 mC/cm was found under a field of 75 kV/cm at 25 °C. Phase analysis revealed a single phase perovskite structure with a hexagonal unit cell with a55.77 Å and c57.08 Å. ^110& selected area electron diffraction patterns revealed superlattice reflections along the ^111&. High resolution Z-contrast imaging was used to study the local ordering and the origin of the relaxational polarization. © 2000 American Institute of Physics. @S0021-8979~00!09017-4#
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