Ternary oxo-selenates

Fig. 6. Chains ofthe composition J)[Pr(Se04)4/2(H20)5] (top) and ( [Ce(Se04)4/2(H20)5] layers (bottom) in the ternary oxo-selenate(VI) pentahydrates (NH4)Pr(Se04)2-5H20 and RbCe(Se04)2 5H20.

Consequently, we will start with the description of oxo-selenates(VI) in the first part of this chapter, and then move on to the major part of the article which is dedicated to oxo-selenates(lV). The oxo-selenate(Vl) section provides the description of various binary compounds in the first part (section 2.1), and will discuss the respective ternary phases in the second part (section 2.2). Among the properties of oxo-selenates(VI) (section 2.3), the thermal behavioitr firms out to the best irrvestigated one. The oxo-selenate(IV) section also starts with the binary species (section 3.1). These are the best investigated oxo-selenates so far, so that more details can be given, for example on synthesis (section 3.1.1) of the R2(Se03)3 type compoimds (section 3.1.2) which are completely known. Subsequent sections are devoted to the anionic (section 3.2) and cationic (section 3.3) derivatives of oxo-selenates(IV) and finally, properties of oxo-selenates(lV) will be discussed. The last section summarizes orrr present knowledge of mixed-valent oxo-selenates(IVA ) which, unfortunately, remairts limited. 

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