Abstract:
The two ternary zinc/manganese- tin-oxygen spinel systems (AB2X4) are amongst some of the most widely researched areas of inorganic materials chemistry due to their technical importance stemming from properties such as high electron mobility, temperature stability, chemical durability, conductivity and reflectivity. A desirable aspect of these spinels is their ability to tailor particular features for different uses, by introducing doped metals to form mixed-transition metal oxide (MTMO) spinels. The aim of the thesis is to investigate the spinels Zn2SnO4 and Mn2SnO4 further by systematically substituting magnetically active Fe into each to produce a new collection of spinel compounds (Zn2-xFex)SnO4 and (Mn2-xFex)SnO4 (0 ≤ x ≤ 2). Cation distribution between octahedral and tetrahedral sites in spinels is a critical aspect in the determination and tuning of their magnetic and electrical properties. We want to find out the exact mechanism of Fe substitution, how much Fe and in what oxidation state is being substituted and where exactly in Zn2SnO4 and Mn2SnO4 is it being placed and the factors that determine this. The results are interesting because Fe ions have a diverse range of possible oxidation states and crystallographic sites and will provide an opportunity to investigate the magnetic effects of substituting Fe into specific unit cell sites. The analyses of our results, via Rietveld refinements of our laboratory and synchrotron X-ray powder diffraction data, as well as neutron powder diffraction data suggest that there are multiple substitution pathways for the (Zn2-xFex)SnO4 and (Mn2-xFex)SnO4 spinel compounds that are dependent upon how much Fe is substituted into the system.
