Abstract
Iron phosphates are a wide group of compounds that possess versatile applications. Their properties are strongly dependent on the role and position of iron in their structure. Iron, because of its chemical character, is able to easily change its redox state and accommodate different chemical surroundings. Thus, iron-phosphate crystallography is relatively complex. In addition, the compounds possess intriguing magnetic and electric properties. In this paper, we present crystal structure properties of a newly developed iron-phosphate compound that was obtained by devitrification from iron-phosphate glass of pyrophosphate stoichiometry. Based on X-ray diffraction (XRD) studies, the new compound (Fe7P11O38) was shown to adopt the hexagonal space group P63 (No. 173) in which iron is present as Fe3+ in two inequivalent octahedral and one tetrahedral positions. The results were confirmed by Raman and Mössbauer spectroscopies, and appropriate band positions, as well as hyperfine interaction parameters, are assigned and discussed. The magnetic and electric properties of the compound were predicted by ab initio simulations. It was observed that iron magnetic moments are coupled antiferromagnetically and that the total magnetic moment of the unit cell has an integer value of 2 µB. Electronic band structure calculations showed that the material has half-metallic properties.
Highlights
Iron phosphates are a wide group of compounds that possess versatile applications
The X-ray diffraction (XRD) pattern of the devitrified material (Fig. 1) is characterized by intense reflections of the crystalline compounds and a relatively low background with a characteristic broad halo around 2Θ≈20° that may originate from the residual glassy phase
The obtained pattern was quantitatively analyzed by comparing it with XRD patterns from databases (COD, AMMIN, ICCD, PDF-4)
Summary
Iron phosphates are a wide group of compounds that possess versatile applications. Their properties are strongly dependent on the role and position of iron in their structure. Iron-phosphate compounds, as well as glasses (IPG) are important materials, which can find applications in different fields such as biomedical and electrical devices, waste immobilization, optical instruments, e tc[1,2,3,4]. Their properties depend on the structure of the phosphate network and the role and atomic position of iron. The amount of Fe2+ depends mainly on the preparation conditions[8] This leads to a very complex crystallography of the FeO-Fe2O3-P2O5 system with more than 20 different crystalline iron-phosphate phases present at ambient pressure[9]. The process follows from the surface to the bulk of the material, and FePO4 can be detected only on s urface[18]
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