Stress required to densify a low-fire NiCuZn ferrite under constrained sintering

The effect of uniaxial stress on the densification behavior of a low-fire NiCuZn ferrite during constrained sintering of a multi-layer structure of a ferrite tape and a pure alumina tape has been investigated. Compared with free sintering, the densification of ferrite becomes significantly reduced and slowed down under pressure-less constrained sintering. To enhance the constrained densification of ferrite in the temperature range required for free sintering, uniaxial stress applied in the thickness direction is needed. The required uniaxial stress to densify ferrite under constrained sintering to reach a relative sintered density of > 95% decreases from 1100-1300 kPa at 900 degrees C to 250-450 kPa at 1000 degrees C. Moreover, no significant grain growth is found when the ferrite is densified under pressure-assisted constrained sintering.