Microstructural and magnetic properties of self-biased strontium hexaferrite thick films by two-step sintering

摘要

SrFe_(12)O_(19) hexaferrite thick films were prepared by tape casting method followed by a two-step sintering process. X-Ray diffractometer, field emission scanning electron microscope and vibrating sample magnetometer were used to investigate the microstructure and magnetic properties of samples. Results show that high density films with nanocrystalline grains, high crystallographic c-axis orientation of crystals perpendicular to the film plane with high squareness (M_r/M_s = 0.93) and moderate coercivity (H_c = 3,750 Oe) can be obtained with two-step sintering. Grains growth is controllable by this sintering method. The average grain size of the films strongly depends on final stage of sintering and quality of starting powders and ranging between 0.5 and 10 μm. The thick films with starting powders from coprecipitation method are denser with smaller grain size rather than those with starting powders from solid state reactions. This work reveals the feasibility of fabrication of thick hexaferrite films with a simple and effective method for next generation of self-biased planar microwave devices.