The effect of cordierite additives on microwave magnetic properties of LiZn ferrites

The influence of firing temperature and cordierite additive on the microstructures and hysteresis loop and microwave magnetic properties of LiZn ferrites has been investigated. The addition of cordierite was found to help densification and grain growth of the LiZn ferrite, depending on firing temperature and the content of cordierite. Microstructural observations revealed that the cordierite tended to segregate at grain boundaries more apparently with increasing the content of cordierite, and not to crystallize even at a relatively high temperature of 1150 °C. Several magnetic parameters including coercive force H_c, spin wave line width ΔH_k and 3dB resonance line width ΔH_3dB were believed to depend on microstructural characteristics such as grain size, porosity and grain boundary segregation. When the sample was fired at 1000 °C, for example, ΔH_3dB showed a minimum value of ∼520 Oe with the addition of 0.5 wt.% cordierite and gradually increased with further additions presumably due to decreased grain size and more glass segregation at grain boundaries.