Structural and magnetic properties of Bi0.80Ba0.20Fe1-xTixO3 ceramics prepared by ball milling technique

Abstract

The Bi0.80Ba0.20Fe1-xTixO3 (0≤x≤0.10) ceramics samples are synthesized by solid state reaction and planetary ball milling technique. The structural, magnetic and electrical properties have been investigated over a wide range of temperature and magnetic field. It is observed that astructural phase transformation has occurred for 20% Ba doped BFO. The rhombohedral crystal structure is transformed into a pseudo cubic structure causing a change in the unit cell volume and also that of the nanocrystalite. The FESEM images show that the grains are segregated into different clusters with a wide range of size distribution from 100-300 nm. The composition was later doped with Ti to observe the effect of Ti doping on the magnetic and electrical properties of the material. The dc magnetization shows that Ba doped Bismuth Ferrite samples is ferromagnetic with a significant magnetization. However with increasing Ti concentration the magnetization has decreased. The low temperature hysteresis shows diamagnetism for 10% Ti concentration which is regarded as a magnetic phase transition making this composition an interesting material for technological application. It is observed that the highest magnetization is achieved for 20% Ba doped BFO which indicate that there is a possible suppression of long cycloidal spin structure resulting in an enhanced magnetization. The introduction of Ba2+ ion at Bi3+ site is likely to induce oxygen vacancy which is one of the origins of leakage current. The change in orientation of FeO6 due to the change of coordination of Fe is also assumed to be another origin of leakage current. It is predicted that the introduction of Ti4+ ion at the Fe site compensates for the oxygen vacancy and reduce the leakage current. In addition the introduction of Ti4+ is likely responsible for the increased resistivity of the material. The measured ac dielectric constant, dielectric loss, ac permeability at different temperatures show a strong frequency dependent behavior. The room temperature dielectric constant and dielectric loss factor have shown high values at low frequency and have decreased rapidly with increasing frequency.