Submicron pre-sintering grain size effects on the microstructure and magnetic properties of hot-press sintered barium hexaferrite thick films

Grain size plays an important role in affecting the physical properties of ceramics. In this work, the effects of pre-sintering grain size G0 of BaFe12O19(BaM) on the microstructure and magnetic properties of hot-press sintered BaM thick films were studied. Results show that reducing G0 in submicron scale leads to notable decreases in grain growth activation energy and final sintered grain size. Smaller G0 makes BaM grains easier to be aligned by magnetic field before sintering and less magnetic domain walls in the sintered film. This increases the c-axis orientation, out-of-plane remanence ratio SQ (> 0.9) and coercivity of sintered film. Moreover, the zero-field ferromagnetic resonance linewidth & UDelta;H decreases 54% as G0 reduces from 1 mu m to 0.3 mu m. This is attributed to the increased film uniformity with larger SQ and film density Drel at smaller G0. The above findings enable better understanding on the role of G0 in improving the magnetic properties of hot-press sintered BaM and other hexaferrite thick films for self-biased microwave devices.