Abstract
The title compound, CaNi2Fe(PO4)3, was synthesized by solid-state reactions. Its structure is closely related to that of α-CrPO4 in the space group Imma. Except for two O atoms in general positions, all atoms are located in special positions. The three-dimensional framework is built up from two types of sheets extending parallel to (100). The first sheet is made up from two edge-sharing [NiO6] octa-hedra, leading to the formation of [Ni2O10] double octa-hedra that are connected to two PO4 tetra-hedra through a common edge and corners. The second sheet results from rows of corner-sharing [FeO6] octa-hedra and PO4 tetra-hedra forming an infinite linear chain. These layers are linked together through common corners of PO4 tetra-hedra and [FeO6] octa-hedra, resulting in an open three-dimensional framework that delimits two types of channels parallel to [100] and [010] in which the eightfold-coordinated CaII cations are located.
Highlights
The title compound, CaNi2Fe(PO4)3, was synthesized by solid-state reactions
Except for two O atoms in general positions, all atoms are located in special positions
Octahedra, leading to the formation of [Ni2O10] double octahedra that are connected to two PO4 tetrahedra through a common edge and corners
Summary
Phosphates belonging to the alluaudite (Moore, 1971) or to the -CrPO4 (Attfield et al, 1988) structure type exhibit interesting physical and chemical properties. These compounds have many promising applications such as use as positive electrodes in lithium and sodium batteries (Kim et al, 2014; Huang et al, 2015) or as catalysts (Kacimi et al., 2005). Over the last few years, phosphate-based compounds crystallizing in the -CrPO4 or alluaudite structure types have been investigated by us. (Alhakmi et al, 2013) and PbMnII2MnIII(PO4) (Assani et al., 2013), the magnesium phosphate NaMg3(PO4)(HPO4) In a continuation of the latter preparation route, we have investigated pseudo-quaternary systems MO–NiO–Fe2O3–P2O5 (M represents a divalent cation) and report here on the synthesis and crystal structure of the title compound, CaNi2Fe(PO4)
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