Complex dielectric behaviours in BiFeO3/Bi2Fe4O9 ceramics

The complex dielectric permittivity of a sintered ceramic tablet consisting 70.5% BiFeO3, 27.7% Bi2Fe4O9 and 1.8% Bi25FeO40 was analyzed as function temperature from – 120 °C to 230 in two separate runs. results reveal complicated response with activated relaxation processes. first is purely Arrhenius related hopping processes between Fe3+ Fe2+ traps induced by oxygen vacancies at grain boundaries. second process more unusual. Its characteristic time follows quasi-Vogel–Tammann–Fulcher behavior fitting the critical point estimated $${ T}_{0}=766 K$$ . It absent run. can be dynamic rearrangements domain boundaries different crystallites ceramic. also ferroelectric phase transition that decayed repeated heating cycles tablet. pure BiFeO3 1098 K, whereas current show it 373 K. origin this reduction traced locally strains on mainly because unit cell size mismatch Bi2Fe4O9.