Kaikan L. Synthesis, structure and physical properties of nanosized substituted lithium ferrites.

In this work carried out the complex research of influence of synthesis conditions by a method of sol-gel of auto combustion on structure, morphology and physical properties of nanosized lithium ferrites-spinels. Established the role of substitution of Cobalt, Nickel, Aluminum and Magnesium ions for improving the properties of synthesized materials and their ability to adapt for practical use. It was found that modifications of the synthesis conditions (selection of the optimal metal/fuel ratio, pH of the reaction medium and the chelating additive) leads to a more intense combustion reaction, and reduces the duration of the process, which decreases particle agglomeration and porosity of the final product. Substitution of cobalt ions leads to the transformation of the structure from the ordered spinel of the spatial group P4332 to the disordered one, of Fd3m group. The magnetic properties of ferrite replaced by Cobalt ions vary from magnetically soft to magnetically hard. It is shown that the introduction of Ni2+ ions instead of Fe3+ leads to important modifications of the electrical properties of the samples, in particular the mechanism or type of conductivity (from n- to p-type). The change in electrical conductivity in Li-Ni ferrites with temperature is presented based on a narrow-band conductivity mechanism and is associated with the formation of small polarons. Substitution of aluminum ions leads to change in the conductive and dielectric properties of lithium ferrite. Moreover, the temperature dependence of the conductivity and the actual part of the dielectric constant in the temperature range 350 - 400K is anomalous, which gives grounds to affirm the manifestation of ferroelectric properties in this temperature range. In the case of replacement of lithium ferrite with magnesium ions, a nonmonotonic dependence of magnetic characteristics on the content of doped ions was established. It is shown that the combination of synthesis conditions and the amount and type of substituted ions allows to systematically change the physical properties of the synthesized material.