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A one-dimensional conductivity barrier model is introduced to describe the dielectric response and conductivity of BiFe03 (BFO) and (Bio.95Ndo.o5)Fe03 (BFO-5%Nd) ceramics as functions of temperature and frequency. Good qualitative fits of conductivity and dielectric permittivity in the intermediate temperature region (500-800 K) are obtained with intrinsic barriers of B=8700 K (for BFO) and B=8400 K (for BFO-5%Nd), and extrinsic barriers of ,1=2500 K (for BFO and BFO-5%Nd). The phase-shifted conductivity is responsible for a step-like dielectric relaxation in the region of 500-800 K. The experimental conductivity departs from the conductivity-barrier model fit below 650 K. This deviation is likely caused by the magneto-electric coupling near the antiferromagnetic paramagnetic transition. This work suggests that the 5% mole Nd-substitution can stabilize the perovskite structure in BFO ceramic.

Phase transitions, dielectric permittivity, and conductivity of (Bi 1-x Ba x)(Fe 1-x Ti x)O 3 (x = 0.05 and 0.1) [BFO-(Ba,Ti)] multiferroic ceramics have been studied as functions of temperature and frequency. In situ synchrotron x-ray diffraction revealed rhombohedral-cubic transitions in the temperature ranges 760-780 • C in BFO-5%(Ba,Ti), and 720-750 • C in BFO-10%(Ba,Ti). A one-dimensional barrier model with intrinsic barriers B every lattice constant a and extrinsic barriers B + is introduced to describe the dielectric response and conductivity. This work revealed that (Ba,Ti) substitutions can enhance the intrinsic barriers and reduce the hopping rate of charge carriers, thereby giving the desired effect of decreasing the conductivity.