Rate of Transition from the Disordered Lattice Structure to the Ordered One in the Lithium Ferrite, Li<sub>0.5</sub>Fe<sub>2.5</sub>O<sub>4</sub>

Abstract

The rate of transition from the disordered lattice to the ordered lattice in the lithium ferrite has been found to depend strongly on the preparation conditions of the ferrite sample. The present study was done to investigate the governing factors of the transition rate. Various samples of ferrite were made by changing the preparation conditions variously and their long-range order parameter was measured by X-ray diffraction. The results obtained are as follows.1) The order-disorder transition temperature of the lithium ferrite was found to be 725°C in a flowing atmosphere of nitrogen and to be 750°C in a flowing atmosphere of oxygen.2) The disorder-to-order transition proceeds at an observable rate in a temperature range from 400°-450°C to the transition temperature. In a temperature below 400°-450°C the transition scarcely proceeds.3) The experimental results show that the disorder-to-order transition rate is governed by the oxygen content in the ferrite sample. The transition rate becomes larger in proportion to the oxygen content.4) It is considered that the concentration of cation vacancies on B-sites (octahedral sites) of the ferrite increases with the oxygen content, and through those vacancies the exchange of lattice position between Li+ and Fe3+ ions on B-sites will easily proceed to complete the transition.