Low Temperature Broad Band Dielectric Spectroscopy of Multiferroic Bi6Fe2Ti3O18 Ceramics
2016
In the present research the tool of broadband dielectric spectroscopy was utilized to characterize dielectric behavior
of Bi6Fe2Ti3O18 (BFTO) Aurivillius-type multiferroic ceramics. Dielectric response of BFTO ceramics was studied in the
frequency domain (Δν=0.1Hz – 10MHz) within the temperature range ΔT=-100°C – 200°C. The Kramers-Kronig data
validation test was employed to validate the impedance data measurements and it was found that the measured impedance
data exhibited good quality justifying further analysis. The residuals were found to be less than 1%, whereas the “chi-square”
parameter was within the range χ2~10-7-10-5. Experimental data were analyzed using the circle fit of simple impedance arc
plotted in the complex Z”-Z’ plane (Nyquist plot). The total ac conductivity of the grain boundaries was thus revealed and
the activation energy of ac conductivity for the grain boundaries was calculated. It was found that activation energy of
ac conductivity of grain boundaries changes from EA=0.20eV to EA=0.55eV while temperature rises from T=-100°C up to
T=200°C. On the base of maxima of the impedance semicircles (ωmτm=1) the relaxation phenomena were characterized in
terms of the temperature dependence of relaxation times and relevant activation energy was calculated (EA=0.55eV).
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