Preparation and microwave absorption properties of BiFeO_3 and BiFeO_3/PANI composites

摘要

BiFeO_3(BFO) particle was successfully synthesized by normal citric acid sol-gel method and the size of BiFeO_3 particle is about 200 nm. BiFeO_3/polyaniline (PANI) composites with the different weight ratio were synthesized by in situ emulsion polymerization. The citric acid doped PANI is fibrous and form a loose structure outside the BFO particle. With the increasing of PANI, the conductivity value of composites are increasing to 9.34 × 10~(−2) S/cm. Moreover, the permittivity also enhance with the increasing of conductivity, which contribute to the improvement of dielectric loss. Microwave absorbing properties were investigated with a vector network analyzer in 1-18 GHz. The minimum reflection loss (RL) value is about −40.2 dB at 8.3 GHz when the thickness is 3.5 mm, and the maximum bandwidth less than −10 dB is 3.5 GHz (from 13.5 to 18 GHz) at the thickness of 2 mm. 3 mm millimeter-wave-attenuation properties were also tested, and the maximum attenuation value of BFO/PANI composites reach 15.71 dB. The composites can dissipate microwave energy into heat effectively by dielectric relaxation because of the suitable conductivity. The interface scattering and multiple reflections also play a important role because of the increasing of a loose structure. The BFO/PANI composite can be taken as a promising lightweight and multiband microwave absorber.