Materials Engineering Research

In the present work, pure BaTiO_3, pure Ni_0.6Zn_0.4Fe₂O₄ and (1-x)BaTiO₃-xNi_0.6Zn_0.4Fe₂O₄ (where x = 0.15, 0.25 & 0.35) multiferroic composites were synthesized through solid-state sintering scheme. Structural, microstructural, ferroelectric, and ferromagnetic analysis was performed. Both tetragonal perovskite phase (for BaTiO₃ ferroelectric phase) and cubic spinel ferrite phase (for Ni_0.6Zn_0.4Fe₂O₄ ferromagnetic phase) were simultaneously presented within each composite. The ferrite phase exhibited a smaller crystallite size compared to the ferroelectric phase. All of the composites demonstrated homogenous irregular-shaped grains. The measured average grain size for 0.85BaTiO₃-0.15Ni_0.6Zn_0.4Fe₂O₄, 0.75BaTiO₃-0.25Ni_0.6Zn_0.4Fe₂O₄, 0.65BaTiO₃-0.35Ni_0.6Zn_0.4Fe₂O₄ were 364.14 nm, 378.46 nm and 351.62nm, whereas the density values were 3.04g/cm³, 3.20g/cm³ and 3.13 g/cm³ for x = 0.35, 0.25, 0.15 respectively. However, the heterogenous microstructure was observed for all of the compositions. The composites exhibited an oval-shaped lossy capacitor hysteresis loop. However, 0.75BaTiO₃-0.25Ni_0.6Zn_0.4Fe₂O₄ composite showed the highest remnant polarization (11.613 μC/cm²) and coercive field value (1.526 kV/cm), ensuring its usability for switching applications. In addition, 0.75BaTiO₃-0.25Ni_0.6Zn_0.4Fe₂O₄ also exhibited the maximum saturation (M_s= 1.732 emu/g) and remnant magnetization (M_r= 0.025 emu/g) among the composites. Nevertheless, all of the composites derived 'wasp-waisted' hysteresis loops due to the presence of either superparamagnetic (SPM) particles or a mixer of a single domain (SD) and superparamagnetic particles.

In this study, zinc oxide (ZnO) nanoparticles (NPs) were first synthesized using co-precipitation method in the presence of Zn(NO₃)₂.6H₂O precursor and calcined at different temperature of 450 ^oC and 1000 ^oC. Samples were then characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The XRD study revealed the hexagonal wurtzite structure for annealed samples. SEM images showed tthat he morphology of the ZnO NPs changed from sphere-like shape to polygon shape by increasing temperature. The exact size of NPs were measured by TEM analysis about 40 nm for as-prepared samples. The EDS analysis demonstrated an increasing level of Zn element from 28.5 wt% to 50.8 wt% for as-synthesized and annealed samples, respectively.