Effect of La substitution on conductivity and dielectric properties of Bi_1-x La_x FeO₃ ceramics: an impedance spectroscopy analysis

Abstract

Bismuth ferrite (BFO) and La-substituted BFO with composition Bi_1-x La_x FeO₃ (x=0.05, 0.1 and 0.15) (BLFOx=0.05-0.15) ceramics were prepared using the solid state reaction route. A structural phase transition from rhombohedral phase to triclinic phase was observed for BLFO_x=0.05-0.15 ceramics. Modulus spectroscopy reveals the deviation of dielectric behavior from ideal Debye characteristics and the dependence of conductivity on ion hopping in BFO and BLFO_x=0.05-0.15 ceramics. The conductivity of the BFO ceramics decreases for La content of 5 mol%, followed by a subsequent increase with 10 and 15 mol% of lanthanum doping. The typical values of the activation energies at high temperature reveal the contribution of short range movement of doubly ionized oxygen vacancies to the conduction process in BFO and BLFO_x=0.05 ceramics. Both short range and long range motion of oxygen vacancies are responsible for large conductivity in BLFO_x=0.1 and 0.15 ceramics.