Structural, magnetic and dielectric properties of Sr and V doped BiFeO3 multiferroics

Bi0.85Sr0.15FeO3 (BSFO), Bi0.85Sr0.15Fe0.57V0.03O3 (BSFVO1) and Bi0.85Sr0.15Fe0.95V0.05O3 (BSFVO2) ceramics were synthesized by solid state reaction method. X-ray diffraction studies and Rietveld refinement results indicate that all the samples crystallized in rhombohedrally distorted perovskite structure. The remnant magnetization and coercive field of BSFVO2 were greatly enhanced in comparison with BSFO. The enhancement of remnant magnetization was attributed to collapse of the spiral spin structure caused by change in bond length and bond angles of BSFO on V substitution. The enhanced value of coercive field might be attributed to decreased grain size with V substitution. BSFO sample shows dispersion in dielectric constant (epsilon') and dielectric loss (tan delta) values in lower frequency region. With V doping this dispersion is reduced resulting in frequency independent region. Dielectric anomaly peak due to charge defects in BSFO sample is also suppressed significantly on V substitution. BSFVO2 sample shows almost temperature stable behavior in e and tan 6 in the studied temperature range. Temperature dependence of index 's' of power law suggests that overlapping large polaron tunneling model is applicable for describing the conduction mechanism in BSFO sample while small polaron tunneling model is appropriate for BSFVO1 and BSFVO2 samples in the studied temperature range. (C) 2015 Elsevier B.V. All rights reserved.