Enhanced magnetoelectric effect in Lead-Free piezoelectric BaZr0.2Ti0.8O3 − 0.5 Ba0.7Ca0.3TiO3 and Fe-rich magnetostrictive Co0.8Fe2.2-xDyxO4 nanocomposites for energy harvesting applications

Abstract

The design, discovery and development of magnetoelectric (ME) composites with enhanced properties and performance opens up further opportunities to explore new scientific aspects and to develop next-generation electromagnetic devices. Nevertheless, the engineered complex ME composites with multi-phase interfacial chemistry have rarely been reported. In this context, in the present work, enhanced magnetoelectric phenomenon reported for the ME-composites made using lead-free ferroelectric phase BaZr0.2Ti0.8O3–0.5Ba0.7Ca0.3TiO3 (BZT-BCT) and magnetostrictive phase Co0.8Fe(2.2-x)DyxO4 (CFDO). The ME composites were synthesized by varying the magnetostrictive CFDO phase, where Dy(x) varied as x = 0.000(ME1), 0.025 (ME2), 0.050 (ME3) and 0.075 (ME4). The effect of varying CFDO phase on the structure, morphology, microstructure, density, piezoelectric, dielectric, ferroelectric and magnetoelectric properties of the ME-composites is evaluated. X-ray diffraction analyses of all ME-composites confirm the tetragonal structure of the BZT-BCT ferroelectric phase and spinel cubic structure of the CFDO ferrimagnetic phase. Raman spectroscopic analyses also confirm and validate the respective phases with a clear signature presence of the characteristics modes. Granular, dense microstructure with a uniform particle size distribution evidenced in scanning electron microscopy imaging analyses. The physical density measurements indicate that the ME composites attain a density in the range of 6.0–6.4 g/cm3; density increases with increasing CFDO phase. Frequency dispersion profiles of the dielectric constant exhibit a maximum dielectric constant for ME1 composite while a sharp decrease in dielectric constant at higher frequencies is noted with increasing CFDO phase in the ME-composites. Ferroelectric properties evaluated by measuring the polarization (P) – electric field (E) hysteresis loops at 300 K indicate the presence of typical P-E loops in all ME composites confirming that the ferroelectric properties are retained even after combining with the magnetic phase. The ME4 composite demonstrate a 0.573 squareness ratio, which is useful for multistate memory device applications. The ME4 composites further characterized by a moderately higher remnant polarization (Pr = 2.24 µC/cm2). All the synthesized ME-composites are promising for permanent memory storage device (FeRAM) applications. Piezoelectric coefficient measurements indicate a maximum piezoelectric coefficient of 116 pC/N for the ME4 composite while the ME-coefficient measurements demonstrate higher ME-coefficients of 250 mV/(cm-Oe) for ME2 composite. Based on the comprehensive and comparative studies of the ME-composites with variable magnetostrictive phase, the structure-chemistry-property correlation in these ME-composites established for possible applications in electromagnetic devices and energy harvesting applications.