Investigation on coupling between ferro-orderings and energy harvesting properties of nickel ferrite and strontium modified barium titanate composites

Environment-friendly, low power-consuming magnetoelectric composites possess the interesting coupling between various ferro-order parameters and find applications in magnetic sensors, waveguides, transducers, spintronics, four-state memory devices, etc. The particulate composites (x)NiFe2O4–(1 − x)Ba0.9Sr0.1TiO3 were prepared using the hybrid sol-gel method using the conventional ceramic double-sintering method. The ferromagnetic nickel ferrite crystallized into a cubic crystal structure whose x-ray diffraction (XRD) peaks could be indexed to F d 3 ¯ m space group. The ferroelectric strontium-substituted barium titanate crystallized to a tetragonal crystal structure with P 4 m m space group. Presence of both crystal symmetries and elemental compositions as per the proposed stoichimetry were observed from experimental results (XRD and electron microscopy techniques). Koop's phenomenological theory could be employed to explain the impedance spectra in the range of 1 kHz to 1 MHz. The effect of Maxwell–Wagner polarization and space charge polarization on the dielectric properties of composites have been observed. The Arrott plot technique successfully explains the suitability of composites for high-energy storage applications. The coupling between both ferro-orderings has been revealed from the magneto-dielectric curves and its dependency on the microstructure has been observed. The magnetocapacitance increased with the increase in NiFe2O4 composition in the (x)NiFe2O4–(1 − x)Ba0.9Sr0.1TiO3 composite. The 30% NiFe2O4 in (x)NiFe2O4–(1 − x)Ba0.9Sr0.1TiO3 composite exhibited overall better energy harvesting (η = 62.9%) and magnetodielectric properties (MC = 1.4%, MI = 20% at 1 kHz).