Structural, electrical, magnetic and magnetoelectric properties of (1−y) [Ba0.6−xCaxSr0.4Zr0.25Ti0.75O3] + (y) [(Li0.5Fe0.5)0.4Ni0.18Cu0.12Zn0.3Fe2O4] composites

Abstract

Magnetoelectric composites having the nominal composition of (1-y) [Ba0.6-xCaxSr0.4Zr0.25Ti0.75O3] (BCSZTO) + (y) [(Li0.5Fe0.5)0.4Ni0.18Cu0.12Zn0.3Fe2O4] (LNCZFO) (x = 0.0, 0.1, 0.2 and y = 0.2, 0.4, 0.6, and 0.8) were synthesized by the solid state reaction method and sintered at 1200 °C for 3 h. The X-ray diffraction analysis confirms the coexistence of tetragonal perovskite BCSZTO and spinel LNCZFO phases with Ba6T17O46 as impurity phase. Microstructural and quantitative elemental of the samples were carried out by Field Emission Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectroscopy. Low frequency dielectric dispersion is attributed due to Maxwell-Wagner interfacial polarization arising from the interface of the two phases in agreement with Koop's phenomenological theory. Frequency independent behavior of dielectric constant at higher frequencies is attributed due to the inability of electric dipoles to follow the first variation of the alternating applied electric field. The dielectric constant decreases with the increasing Ca2+ concentration which is attributed due to the increased resistivity. Maxima in dielectric loss (tanδ) are appeared when the hopping frequency of electrons between different ionic sites becomes nearly equal to the frequency of the applied field. AC conductivity of the composites follows Jonscher's universal power law and the conduction mechanism is attributed due to small polaron hopping. AC conductivity increases with the increase of Ca2+ concentration. The composite materials are found to exhibit excellent frequency dependence and increases with the ferrite concentration. The permeability decreases with the increase of Ca2+ concentration which is attributed to the smaller grain size and increased magneto crystalline anisotropy. The quality factor increases with the Ca2+ ions substitution on account of the high resistive boundary segregation. The magnitude of magnetoelectric (ME) voltage coefficient increase linearly with the increase of the applied filed may be attributed to the nominally linear gradient of magnetostriction with respect to magnetic field. The magnetoelectric coefficient of the composites increases gradually as the increase in the ferrite content which is attributed due to the increase of the mechanical deformation in the magnetostrictive phase. An optimal magnetoelectric voltage coefficient of ∼1.16 V cm−1 Oe−1 is obtained for x = 80 wt% (C-series composites) at room temperature.