IMF2017

Electrical conductivity results for of BiFeO₃ ceramics obtained by spark plasma sintering and synthesized by the organic nitrate precursors combustion are presented.. The average size of particle estimated from the diffractograms are ~ 50 nm. The ac - conductivity measurements were conducted in 1 kHz - 10 MHz frequency range over a temperature range of 25 - 500 °C. It is shown that σ_ac (ω) obeys a power law of ω^s, where s < 1. At temperatures > 350 °C and frequencies of > 1 MHz conductivity passes through a maximum, and with increasing frequency the conductivity maximum temperature is shifted to lower temperatures. The conductivity has the thermally activated character. In the investigated temperature range the three overlapping processes are involved in the relaxation conductivity: i) in the temperature range 25 - 150 °C with E_a = 0.46 - 0.042 eV; ii) in a temperature range of 150 - 350 °C with E_a = 0,65-0,11 eV and iii) at temperatures > 350 °C with E_a = 0,96 - 0,76 eV. The activation energy E_a decreases with increasing frequency. The low-frequency conductivity is identified with the dc conductivity. At frequencies > 100 kHz conductivity behavior can be interpreted in the representation of the model correlated barrier hopping (CBH) charge carriers. It is assumed that the hopping mechanism implemented in ceramic grains between the ions Fe²⁺ and Fe³⁺. The role of oxygen vacancies in the conductivity is also discussed.