Ordering Mechanisms in Li Ferrites

This paper describes the ordering mechanisms observed in Li ferrite powder samples with different particle sizes and aggregation states, as well as in sintered pellets. Measurement of ordering rates in the powder samples and observation of chemically etched surfaces of partially ordered pellets indicate that the ordering proceeds by a nucleation-growth mechanism and that the ordering initiates at grain boundaries and prevails into the inner part of the grains. In powder samples, surfaces as well as grain boundaries contribute to the initiation of ordering but their temperature dependences are different. The activation energy of the ordering is calculated to be 192 kj/mol.