Electrical and Magnetic Behavior of Magnetoelectric BaTiO3-NiFe2O4 Composites: Effect of Phase Connectivity of the Constituent Phases

Abstract

The research on magnetoelectric composites has been busted up by their potential applications in microwave devices, sensors, transducers, information storage, spintronics and multiple-state memories. In the present work, ferroelectric BaTiO3 (BT) - ferromagnetic NiFe2O4 (NF) composites were prepared by different powder synthesis route namely solid-state, auto-combustion, and hybrid precipitation to tailor the phase connectivity of the constituent phases. Functional properties (dielectric, piezoelectric, magnetic, magnetodielectric and magnetoelectric) of BT-NF composite thus prepared were studied as a function of NF content in the BT matrix in the range 20-60 mole% as well as the connectivity of the constituent phases. X-Ray diffraction (XRD) studies on sintered (1200 oC/4hr) composites indicates good chemical compatibility of the constituent phases. Microstructural (SEM) study revealed that the powder synthesis technique and the composition of the ferrite phase has a strong influence on the connectivity of the constituent phases. Frequency and temperature dependent dielectric behaviour study confirm the existence of conductivity relaxation in the composite and the constituent phase connectivity have a significant influence on it. The ferroelectric and magnetic behaviour of the composite could be well predicted from the consideration of dilution effect observed in composites materials. Composite properties (magnetocapacitance and magnetoelectric (ME) voltage coefficient) were found to be dependent both on the relative amount of constituent phases, the chemical composition of the ferrite phase and the connectivity of the constituent phases. The highest ME coefficients 1.21 mV.cm-1.Oe-1 was obtained for BT-NF 70:30 composites prepared by hybrid precipitation route. The study suggests that the BT-NF composite prepared by hybrid precipitation technique have the potential for multifunctional application.