Crystal structure of strontium dinickel iron orthophosphate

• Main Authors: Said Ouaatta, Abderrazzak Assani, Mohamed Saadi, Lahcen El Ammari
• Format: Article
• Language: English
• Published: International Union of Crystallography 2015-10-01
• Series: Acta Crystallographica Section E: Crystallographic Communications
• Subjects: crystal structure; transition metal phosphates; solid-state reaction synthesis; SrNi2Fe(PO4)3; α-chromium phosphate
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S205698901501779X

The title compound, SrNi2Fe(PO4)3, synthesized by solid-state reaction, crystallizes in an ordered variant of the α-CrPO4 structure. In the asymmetric unit, two O atoms are in general positions, whereas all others atoms are in special positions of the space group Imma: the Sr cation and one P atom occupy the Wyckoff position 4e (mm2), Fe is on 4b (2/m), Ni and the other P atom are on 8g (2), one O atom is on 8h (m) and the other on 8i (m). The three-dimensional framework of the crystal structure is built up by [PO4] tetrahedra, [FeO6] octahedra and [Ni2O10] dimers of edge-sharing octahedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge-sharing octahedra ([Ni2O10] dimer) linked to [PO4] tetrahedra via common edges while the second layer is built up from a strontium row followed by infinite chains of alternating [PO4] tetrahedra and FeO6 octahedra sharing apices. The layers are held together through vertices of [PO4] tetrahedra and [FeO6] octahedra, leading to the appearance of two types of tunnels parallel to the a- and b-axis directions in which the Sr cations are located. Each Sr cation is surrounded by eight O atoms.