Microstructure, magnetic, and dielectric properties of Co–Zr co-doped hexagonal barium ferrites based on the sintering temperature and doping concentration

In this work, M-type hexagonal barium ferrites co-doped with Co and Zr atoms were prepared by a solid-phase method based on the sintering temperature and doping concentration. First, the influences of the sintering temperature on the crystal structure, microstructure, and magnetic properties of ferrites were studied. The crystallinity of the materials increases with the sintering temperature and obtaining high density and uniform grain size at 1300 °C, which promotes grain-boundary diffusion and suppresses grain-boundary migration. Second, the dependence of the crystal structure, microstructure, magnetic, and dielectric properties of Ba(Co x Zr x )Fe 12−2 x O 19 on the doping concentration ( x  = 0, 0.2, 0.4, 0.6) was investigated at sintering temperature of 1300 °C. The increase of the crystal parameter c with x value reveals that the ions of Co 2+ and Zr 4+ successfully replace the Fe 3+ ions. Additionally, the co-doping ions of Co 2+ –Zr 4+ promote the grain-boundary migration and result in some large size grain (> 20 mm) that appeared and increased with the doping concentration. The magnetic hysteresis loops reveal the saturation magnetization increases from 60.45 to 68.6 emu/g, and the coercivity decreases from 1800 to 190 Oe with the x increased to 0.6. The dielectric properties measurement displays the Co–Zr co-doping can improve the dielectric and reduce the dielectric loss. The highest value of the real part of permittivity ( ε ′) and the lowest value of the imaginary part of permittivity ( ε ″) can be obtained at a doping concentration of x  = 0.4.