Improved electric insulation ability and ferromagnetic property in Nb2O5 doped BiFeO3-based multiferroic ceramics

Abstract

0.675BiFeO₃-0.3BaTiO₃-0.025LaFeO₃-x mol% Nb₂O₅ (x = 0–1.25) multiferroic lead- free ceramics, fabricated by conventional solid-state reaction, were studied to reveal the effects of Nb₂O₅ on the structural, morphology, dielectric, ferroelectric, magnetic and magnetoelectric properties of the BiFeO₃-based ceramics. After the addition of Nb₂O₅, the crystal structure of as-prepared samples remained orthorhombic phase. The doping Nb⁵⁺ ion could be able to inhibit grain growth remarkably and suppress the creation of oxygen vacancies of this ceramics, which resulted in the improvement of electrical insulation by two orders of magnitude. The ferromagnetism was apparently enhanced with increasing content of Nb₂O₅, and the observed remanent magnetization Mr peaked at 0.022 emu/g for x = 1. Suitable amount of Nb₂O₅ could be beneficial to the dielectric properties, with the optimal x at 0.75, with dielectric constant ε_r of 918 at 100 Hz. The observed magnetoelectric coefficient α_ME suggested the existence of magnetoelectric coupling effect in these ceramics. The α_ME value almost decreased after adding Nb₂O₅, possibly due to the obvious degradation of ferroelectric behaviors.