Effect of annealing atmosphere on the structural and electrical properties of BiFeO3 multiferroic ceramics prepared by sol-gel and spark plasma sintering techniques

Phase-pure BiFeO3 powders were synthesized by sol gel technique. Based on these powders, high-density BiFeO3 ceramics were prepared by spark plasma sintering (SPS) at 700 degrees C along with annealing for 2 and 4 h, respectively, at 650 degrees C under atmospheres of air and oxygen. X-ray diffraction analysis revealed that the 4 h-oxygen-annealed sample contained a single rhombohedral perovskite phase while the samples annealed in the other conditions contained small quantities of impurity phases besides the rhombohedral perovskite phase. The relative density of the 4h-oxygen-annealed sample was about 96%, being apparently higher than that of the other samples. In comparison with the 4 h-air-annealed sample, the dielectric constant of the 4 h-oxygen-annealed sample was relatively higher. The activation energy for electrical conduction was about 1.17 eV for the 4 h-oxygen-annealed sample while it was about 0.98 eV for the 4h-air-annealed sample, showing that the former would have a lower room-temperature conductivity (similar to 2.6 x 10(-14) S cm(-1)) than the latter (similar to 2.1 x 10(-13) S cm(-1)). It is therefore anticipated that the oxygen-annealed sample could possess better ferroelectric properties as compared to the air-annealed sample. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.