Dilatometric and kinetic analysis of sintering Li–Zn ferrite ceramics from milled reagents

The impact of mechanical milling of the mixture of Fe₂O₃–Li₂CO₃–ZnO reagents on thermal sintering of lithium–zinc ferrites of Li_0.4Fe_2.4Zn_0.2O₄ composition was studied using X-ray diffraction, dilatometric and kinetic analyses. The dilatometric analysis showed that mechanical pre-activation of the mixture of the initial reagents in a planetary mill reduces the initial shrinkage point and accelerates compaction of ferrite-pressed samples during sintering, which ultimately increases the density of the finished ferrite ceramics. The sintering of lithium–zinc ferrite from a non-milled mixture proceeds in two steps. At the first stage, the samples show linear expansion, and at ~ 720 °C, a sharp shrinkage occurs. The data obtained from milled samples indicate that shrinkage starts at lower temperatures and is in the range of 370–400 °C. This result allows simultaneous synthesis and sintering of lithium–zinc ferrite through one-stage heating of pressed samples to the sintering point. The resulting lithium–zinc ferrite ceramics exhibits high density, specific magnetization and Curie temperature. The kinetic analysis of ferrite compaction was performed, and kinetic parameters and the model to describe this process were found.