Abstract
The powder compact of Ba ferrite was directly sintered by hot isostatic press (HIP). Using HIP, grain growth was successfully controlled and densification was achieved at low temperature. The Ba ferrite powder prepared by coprecipitation was densified to 99.6% without grain growth by sintering at 1000°C for 1 h under 200 MPa. The average grain size of the Ba ferrite obtained was 0.2 µm, which was comparable to the particle size of starting powder. This Ba ferrite revealed 10.3 kJ/m3 in (BH)max. This (BH)max was increased to 14.1 kJ/m3 by annealing the Ba ferrite at 1000°C for 1 h under atmospheric pressure. The improvement of (BH)max is due to the relaxation of the internal stress induced by HIP sintering.
