AC conductivity of BiFeO$_{3}$ ceramics obtained by spark plasma sintering of nanopowder

The structure and electrical properties of BiFeO$_{3}$ ceramics obtained by spark plasma sintering of a nanopowder are investigated. The nanopowder was synthesized by burning of an organic nitrate precursor. The ac conductivity was measured in a frequency range of 1 kHz–10 MHz in a temperature interval of 25–500$^\circ$C. It is established that the temperature conductivity coefficients above and below $\sim$350$^\circ$C significantly differ with both alternating and direct currents. The frequency dependence of the conductivity obeys the Jonscher power law $\sigma\sim\omega^s$, where $s<$ 1. The interpretation of this behavior is given in the framework of the model of correlated hops of charge carriers over potential barriers. It is assumed that the hopping mechanism is realized between Fe$^{2+}$ and Fe$^{3+}$ ions in ceramic grains. The role of oxygen vacancies in the conduction is also discussed.