Stress-induced multiferroic properties of lead-free (1-x)BTNO-(x)CFO nanocomposites

Multiferroic composites of (1 - x)BaTi0.98Ni0.02O3-(x)CoFe2O4 (0 <= x <= 0.06) were prepared through conventional solid-state reaction route. X-ray diffraction (XRD) studies along with the Rietveld refinement endorse the multiphase nature of the nanocomposite samples. The XRD peaks of the tetragonal bare barium titanate and the inverse cubic spinel of cobalt ferrite nanostructures phase can be identified separately. The tetragonality ratio of the bare barium titanate drops with the addition of the guest material, i.e., cobalt ferrite in the ferroelectric matrix. The Fourier transform infrared (FTIR) spectra confirm the main absorption bands near 540-560 cm(-1), corresponding to the metal-oxide absorption band (nu(1) mode), and are related to the stretching modes of the Ti-O bonds. The Raman spectra also signify the two symmetries confirming the nanocomposites' ferroelectric and ferromagnetic phases. The surface morphology studies reveal the hexagonal and spherical shape of the grains in the nanostructures and nanocomposites. The energy-dispersive x-ray spectroscopy (EDX) spectra confirm the presence of all the elements in the samples. The ferroelectricity in the nanocomposite drops due to fluctuations in the valence state of Fe2+/Fe3+ that enhances the leakage current of the nanocomposites. The magnetic moment and dielectric constant of the nanocomposites are enhanced as the guest compound CoFe2O4 is added to the bare BaTi0.98Ni0.02O3. Thus, the simultaneous coexistence of ferroelectric and magnetic ordering at room temperature confirms the multiferroic behavior of the nanostructure and the nanocomposites.