Crystal Chemistry of Novel Oxide Compounds of Se4+ and Se6+

Abstract

This work deals with the synthesis and characterization of novel oxide materials containing selenium in the oxidation states of +4 or +6. The structural types occurring in 33 known oxoselenite minerals have an amazing variety, and cover the whole field from 0D isolated complexes to 3D frameworks, which offer unexploited potentialities in terms of physical properties. This thesis aims to synthetize and investigate new Se based compounds, using methods inspired by mineralogical processes. Information based on original building units assembled into original architectures have been deduced and compared to related inorganic phases of the literature. In the present study, our innovative so-called “geo-inspired” approach is applied in order to obtain complex novel crystalline compounds. This approach assumes emulation and modelling of natural crystal growth processes. Herein, we used either a traditional descriptive procedure based on consideration of the crystal structures in terms of coordinations of cations, or the modern theory of anion-centered tetrahedra developed by the St. Petersburg school of crystallography and the UCCS group of solid-state chemistry in Lille, in cases when the traditional structural interpretation does not reflect basic principles of crystal architecture. Thus, several metal-oxide chemical systems with Se4+/6+ and various metals (Cu+/2+, Ni2+, Co2+, V4+/5+, Mn2+, Fe3+, Pb2+, Bi3+, U6+) were studied in the context of the present work. The thesis contains results of synthetic procedures, and crystal chemical characterization of 39 new metal selenites, selenates, and selenite-selenates. The analogy of selenite groups with phosphites was also investigated. Main results are described with references to more detailed publications given in the appendices.