Structural, dielectric, ferromagnetic, ferroelectric and ac conductivity studies of the BaTiO3–CoFe1.8Zn0.2O4 multiferroic particulate composites

Abstract

Multiferroic particulate composites comprising BaTiO3 as ferroelectric phase and CoFe1.8Zn0.2O4 as ferrite phase with the formula (1−x) BaTiO3–(x) CoFe1.8Zn0.2O4 (where x=10, 20, 30 and 40wt%) are fabricated by the solid state reaction method. To check the phase purity and structure formation, X-ray diffraction (XRD) technique has been used. XRD patterns confirm the formation of the individual phases and the composites. Using scanning electron microscopy (SEM), the morphology of the composites is studied and reveals an increase in grain size with ferrite content. In addition, significant effect of ferrite content on the dielectric, electric and magnetic properties of the composites has also been observed. Variation of dielectric constant (ε׳) and loss tangent (tan δ) with temperature (up to 400°C) and frequency (20Hz–1MHz) have been investigated. Dielectric constant is found to increase as ferrite fraction increases with the appearance of two peaks, one in the lower temperature region and other in the higher temperature region. Peak observed in the low temperature range (120°C–150°C) is ascribed to ferroelectric to paraelectric phase transition of the BaTiO3 phase. The increase in dielectric constant can be attributed to the space charge effect and the hopping conduction mechanism. Besides this, the variation of loss tangent (tan δ) with temperature of the composites exhibits loss peaks. With increasing frequency, all the composites show usual dielectric dispersion. AC conductivity of the composites has been studied as a function of frequency and temperature to understand the conduction mechanism. The observed behavior of the conductivity can be interpreted using a jump relaxation model (JRM). Polarization (P) vs. Electric field (E) and Magnetization(M) vs. Magnetic field (H) loops are measured at room temperature which demonstrates that all the composites exhibit simultaneously good ferroelectric and ferromagnetic properties.