Structures of the two M0.50SbFe(PO4)3 (M = Mg, Ni) phases, abbreviated as [Mg0.50] and [Ni0.50], were determined at room temperature from X-ray diffraction (XRD) powder data using the Rietveld analysis. Both compounds belong to the NASICON structural family. XRD patterns of [Mg0.50] and [Ni0.50] phases were easily indexed with a primitive hexagonal unit cell [P$\overline 3 $ space group, Z = 6] similar to that already obtained for La0.33Zr2(PO4)3. Obtained unit cells parameters are [a = 8.3443(1) Å, c = 22.3629(1) Å], and [a = 8.3384(1), c = 22.3456(1) Å], respectively, for [Mg0.50] and [Ni0.50] phosphates. In both samples, the [Sb(Fe)(PO4)3]− NASICON framework is preserved and a partially-ordered distribution of Sb5+ and Fe3+ ions is observed. Raman spectroscopic study was used to obtain further structural information about the nature of bonding in [Mg0.50] and [Ni0.50] phases.

Crystallographic structures of the three NaSbR(PO4)3 (R = Cr, Fe, In) phases were determined at room temperature from X-ray powder diffraction (XRD) data using the Rietveld analysis. The three compounds belong to the Nasicon structural family. The presence of the (303) reflection in all XRD spectra of NaSbR(PO4)3 shows clearly that all compounds crystallise in rhombohedral system with R3 space group. Na atoms are practically ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a partially-ordered distribution of Sb5+ and R3+ ions within the Nasicon framework. A Raman and Infrared spectroscopic study was used to obtain further structural information about the nature of bonding in NaSbR(PO4)3 (R = Cr, Fe, In) phases.

Crystallographic structures of two new orthophosphates Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 obtained by conventional solid state reaction techniques at 900 °C, were determined at room temperature from X-ray powder diffraction using Rietveld analysis. The two compounds belong to the Nasicon structural family. The space group is R3 for Ca0.50SbFe(PO4)3 and R3c for CaSb0.50Fe1.50(PO4)3. Hexagonal cell parameters for Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 are: a=8.257(1) Å, c=22.276(2) Å, and a=8.514(1) Å, c=21.871(2) Å, respectively. Ca2+ and vacancies in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3 are ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a quasi-ordered distribution of Sb5+ and Fe3+ ions within the Nasicon framework. Thus, in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3, each Ca(3a)O6 octahedron shares two faces with two Fe3+O6 octahedra and each vacancy (◻(3b)O6) site is located between two Sb5+O6 octahedra. In [Ca]M1Sb0.50Fe1.50(PO4)3 compound (R3c space group), all M1 sites are occupied by Ca2+ and the Sb5+ and Fe3+ ions are randomly distributed within the Nasicon framework.

Crystal structures of A0.50SbFe(PO4)3(A=Mn, Cd) phases, obtained by solid state reaction at 920 °C, were determined at room temperature from X-ray powder diffraction (XRD) using the Rietveld method. The structures of the two samples are of the Nasicon-type with the R3 space group. Hexagonal cell parameters for A=Mn and Cd are: a=8.375(1) Å, c=21.597(2) Å and a=8.313(1) Å, c=21.996(2) Å, respectively. From XRD data, it is difficult to unambiguously distinguish between Cd2+ and Sb5+ ions in Cd0.50SbFe(PO4)3 and between Mn2+ and Fe3+ cations in Mn0.50SbFe(PO4)3. Nevertheless the overall set of cation–anion distances within the Nasicon framework clearly shows that the cation distribution can be illustrated by the {[A0.50]3a[◻0.50]3b}M1SbFe(PO4)3 (A=Mn, Cd) crystallographic formula. The divalent A2+ cations and vacancies are ordered within the two positions, 3a and 3b, of the M1 sites. Structure refinements show also a quasi-ordered distribution of Sb5+ and Fe3+ ions within the Nasicon framework. Thus, each A(3a)O6(A=Mn, Cd) octahedron shares two faces with two Fe3+O6 octahedra and each vacancy (◻(3b)O6) site is located between two Sb5+O6 octahedra.