Study On The Electronic And Magnetic Properties Of A-and B-Copped Bi_xFe_1-xO₃Polycrystal Ceramics

Recently, increasing interest have been focused on multiferroic materials, because their potential applications as functional devices. especially that with coexistence of multi ferroic orders (ferromagnetic, ferroelectric or ferroelastic), BiFeO3with perovskite structure with antiferromagnetic and ferroelectric properties is one of the well known single-phase multiferroic at room temperature. However, BiFeO3has some defects, for example low magnetization, high electrical conductance and small magnetoelectronic coupling effect, which are the obstacles for the practical applications. Several routes could be used to solve the above problems, which including the fabrication of a solid solution of BiFeO3with other ABO3-type materials or doping with rare earth elements.In this paper, using modified rapid thermal process we synthesized La0-1Bi0.9Fe03(LBFO) and La0.1Bi0.9CoxFe1-x03(x=0.01,0.03)ceramics with high resistance. We used the X-ray diffraction determined the crystal structure and the phase purity of the samples. The electrical and magnetic properties of the doped-BFO samples werr studied systematically. For La0.1Bi0.9FeO3and La0.1Bi0.9CoxFe1-xO3(x=0.01,0.03) series of samples, Firstly, we found that La doping at Bi site effectively inhibits the generation of the impurity phase. Doped with10at.%LBFO ceramics sintered in the temperature range830-860degrees show very low leakage current and low dielectric loss. Well saturated ferroelectric hysteresis loops and polarization switching currents have been observed. Secondly, the effects of cobalt doping on the electrical conductivity of La0.1Bi0.9Fe1-xCoxO3(LBFCO, x=0,0.01,0.03) ceramics were investigated. XRD investigation shows that the lattice parameters of LBFCO were strongly affected by cobalt doping, and the volume of lattice decreases with increasing cobalt doping concentration. It is found that the leakage current increases with cobalt dopant concentration in LBFCO. On the application of bias voltage LBFCO ceramics with x=0.3exhibits resistive switching effects at room temperature. X-ray photoelectron spectroscopy of LBFCO ceramics show that cobalt dopant is bivalent as an acceptor, which induces an enhancement of oxygen vacancy concentration in LBFCO ceramics. Possible mechanisms for resistive switching effect is discussed on the basis of the interplay of bound ferroelectric charges and mobile charged defects. In addition, we found that the magnetic properties were improved through the Co doping.