Low temperature broad band dielectric spectroscopy of multiferroic Bi6Fe2Ti3O18 ceramics

Abstract

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 (=0.1Hz-10MHz) within the temperature range =-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 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 (mm=1) the relaxation phenomena were characterized in terms of the temperature dependence of relaxation times and relevant activation energy was calculated (EA=0.55eV).