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

0.675BiFeO(3)-0.3BaTiO(3)-0.025LaFeO(3)-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 epsilon(r) of 918 at 100 Hz. The observed magnetoelectric coefficient alpha(ME) suggested the existence of magnetoelectric coupling effect in these ceramics. The alpha(ME) value almost decreased after adding Nb2O5, possibly due to the obvious degradation of ferroelectric behaviors.

Automated summary

The addition of Nb2O5 improved the crystal structure, magnetic and dielectric properties of BiFeO3-based ceramics, while inhibiting grain growth and oxygen vacancies formation. However, there was a decline in ferroelectric behavior when Nb2O5 content exceeded a certain threshold.