Sol-gel auto-combustion synthesis of double metal-doped barium hexaferrite nanoparticles for permanent magnet applications

In the current work, BaZnxZrxFe12-2xO19 (x ​= ​0.00–0.15) sub-micron particles synthesis with the help of the sol-gel auto-combustion technique has been carried out. XRD studies reveal the single BaM (barium hexaferrite of M-type) phase formation and undesirable phases such as BaFe2O4 and α–Fe2O3 absent. The FE-SEM micrographs suggest that the size of grain increases from ≈241 ​nm (x ​= ​0.00) to ​≈ ​280 ​nm (x ​= ​0.15) with a substitution level. The enhancement in grain size with composition has been also confirmed by the dynamic light scattering technique (DLS). The coercivity (Hc) has been continuously decrease from 5363 ​Oe (x ​= ​0.00) to 4211 ​Oe (x ​= ​0.15) with increase in non-magnetic dopant concentration. On the other hand, the saturation magnetization (Ms) value increases from 70.87 emu/g (x ​= ​0.00) to 87.04 emu/g (x ​= ​0.15) with substitution. In the sol-gel auto-combustion synthesis of M-type hexaferrite, fuel plays an important role. It affects the magnetic properties, surface morphology, and calcination temperature of hexaferrite. In the present study, synthesis of Zr4+-Zn2+ doped BaM having a low composition (x ​= ​0.00–0.15) using tartaric acid as fuel is first reported. The enhanced magnetic properties of Zr4+-Zn2+ doped BaM samples over undoped samples can be used in permanent magnet appliances.