Abstract
Spinel soft ferrites such as NiZnFe2O4 are of great interest due to their extensive applications in magnetic-optics, microelectronics, and microwave devices. This study deals with the production of thick Ni0.5Zn0.5Fe2O4 magnetic films (>50 microns) using high velocity oxy-fuel (“HVOF”) thermal spray. With the HVOF process, high density films more than 98% theoretical density were prepared, apparently due to the high velocity of droplets in the process. The influence of the fuel composition on coating structure, deposition efficiency, and magnetic properties of the Ni-Zn ferrite films was investigated. Better magnetic properties were obtained in the as-sprayed film formed with a neutral or oxygen-rich flame. The decomposition of the ferrite material occurred with a fuel-rich flame and resulted in a reduction in magnetic properties. However, the magnetic properties could be improved dramatically after heat treatment. Pellet and toroid samples of these films were produced for evaluation of magnetic properties by saturation magnetization and magnetic permeability. The permeability exhibited a very flat response to high frequencies up to 13 MHz.
