Study on magnetic and dielectric properties of BaTiO3/MnCr0.2Fe1.8O4 composite material

Abstract

BaTiO3 (BT)/MnCr0.2Fe1.8O4 (MCF) composites were prepared by solid state reaction via sol-gel process and sintered at 900 °C for 1 h. The weight percentages of BT/MCF composites were 0/100, 20/80, 40/60, 60/40, 80/20, 100/0. Phase composition and microstructure of the sintered BT/MCF composites were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. Magnetic and dielectric properties of the sintered composites were also studied. The XRD results showed that all sintered composites exhibit the main phase of tetragonal perovskite structure of BT and cubic spinel structure of MCF, that the peak intensity of BT phase increases with increasing BT content. However, BaFe12O19 and α-Fe2O3 extra phases were also observed for all composites. The microstructure of the composites reveals polyhedral grains for MCF phase and BT phase with the grain size of about 0.61–1.93 μm and 0.51–1.12 μm, respectively. All sintered composites present hard ferromagnetic behavior whereas the pure BT and pure MCF are non-ferro/ferrimagnetic and soft magnetic, respectively. Saturation magnetization (Ms) of the sintered composites tends to decrease with increasing BT content, giving the Ms of 6–19 emu/g and Hc of 1.6–2.1 kOe. Dielectric properties of the composites showed that the εr and tanδ of all composites derive from ferroelectric BT behavior and hopping conductivity behavior in ferrite phase which is related to Maxwell-Wagner interface polarization model, leading to dielectric dispersion. The complex impedance spectroscopy indicates the heterogeneous structure consisting of semiconducting grain and insulating grain boundary.