![](/logos/buttonlogos/cross.png)
![](/logos/buttonlogos/cross.png)
inorganic compounds
NASICON-related Na3.4Mn0.4Fe1.6(PO4)3
aDepartment of Inorganic Chemistry, Taras Shevchenko National University, 64 Volodymyrska str., 01601 Kyiv, Ukraine, and bSTC "Institute for Single Crystals", NAS of Ukraine, 60 Lenin ave., 61001 Kharkiv, Ukraine
*Correspondence e-mail: yats_13@ukr.net
The 3.4Mn0.4Fe1.6(PO4)3, was obtained using a method. Its is related to that of NASICON-type compounds. The [(Mn/Fe)2(PO4)3] framework is built up from an (Mn/Fe)O6 octahedron (site symmetry 3.), with a mixed Mn/Fe occupancy, and a PO4 tetrahedron (site symmetry .2). The Na+ cations are distributed over two partially occupied sites in the cavities of the framework. One Na+ cation (site symmetry -3.) is surrounded by six O atoms, whereas the other Na+ cation (site symmetry .2) is surrounded by eight O atoms.
sodium [iron(III)/manganese(II)] tris(orthophosphate), NaRelated literature
For applications and properties of NASICON-related compounds, see: Goodenough et al. (1976); Shimizu & Ushijima (2000
); Veríssimo et al. (1997
); Mariappan et al. (2005
); Arbi et al. (2002
); Moreno-Real et al. (2002
). For details of structural relationships with other compounds, see: γ-Na3Fe2(PO4)3 (Masquelier et al., 2000
); Na4Fe2(PO4)3 (Hatert, 2009
); Na4MgFe(PO4)3 (Strutynska et al., 2012
); Na4NiFe(PO4)3 (Essehli et al., 2011
).
Experimental
Crystal data
|
Refinement
|
|
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2006
); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008
); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008
); molecular graphics: DIAMOND (Brandenburg, 1999
); software used to prepare material for publication: WinGX (Farrugia, 1999
) and enCIFer (Allen et al., 2004
).
Supporting information
https://doi.org/10.1107/S1600536812027584/wm2642sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812027584/wm2642Isup2.hkl
The title compound was obtained during investigation of the melting system Na2O–P2O5–Fe2O3–MnO. A mixture of NaPO3 (12.24 g), Na2CO3 (1.908 g), Fe2O3 (2.4 g) and MnCO3.Mn(OH)2 (3.8 g) was ground in an agate mortar, placed in a platinum crucible and heated up to 1273 K. The melt was kept at this temperature for 3 h. After that, the temperature was cooled down to 973 K at a rate of 10 K/h. The light-violet crystals of (I) were recovered using hot water. The chemical composition of single-crystal was verified using EDX analysis. Analysis found: Na 16.62, Mn 2.14, Fe 7.93, P 14.94 and O 58.37 at%, while Na3.4Mn0.4Fe1.6(PO4)3 requires Na 16.67, Mn 1.96, Fe 7.84, P 14.70 and O 58.82 at%.
For
of the Fe/Mn ratio and the Na-content, SUMP instructions in SHELXL (Sheldrick, 2008) were employed, assuming full occupancy of the (Fe/Mn) site and an average charge of the (Fe/Mn) and Na sites of +9. The refined composition is close to that determined by EDX measurements. The highest remaining peak in the final difference Fourier map is 0.76 A from P1 and the deepest hole is 1.09 Å from the same atom.NASICON-type compounds possess high
chemical stability and attract great interest for application in solid-state electrochemical devices (Goodenough et al., 1976; Shimizu & Ushijima, 2000; Veríssimo et al., 1997; Mariappan et al., 2005; Arbi et al., 2002; Moreno-Real et al., 2002).Herein, the structure of Na3.4Mn0.4Fe1.6(PO4)3, (I), is reported. Compound (I) can be considered as a γ-Na3Fe2(PO4)3 (Masquelier et al., 2000) and belongs to the NASICON structure type.
ofThere are two Na sites (Wyckoff positions 6b and 18e), one mixed occupied Mn/Fe site (12c), one P site (18e) and two O sites (36f) in the γ-Na3Fe2(PO4)3 (Masquelier et al., 2000); 2.010 (6)–2.130 (6) Å in Na4Fe2(PO4)3 (Hatert, 2009); 1.926 (5)–2.037 (6) Å in Na4MgFe(PO4)3 (Strutynska et al., 2012); 1.955 (3)–2.050 (3) Å in Na4NiFe(PO4)3 (Essehli et al., 2011). The P atom has an almost regular tetrahedral coordination, the P—O distances in the PO4 tetrahedra being in the range 1.5244 (16)–1.5346 (15) Å, as is typically observed in NASICON-type phosphates. Two types of sodium atoms occupy the cavities of the framework. The Na1 atoms (s.o.f. = 0.848 (5)) lie on a threefold roto-inversion axis and are surrounded by six O2 atoms in a distance of 2.4546 (15) Å. The Na2 (s.o.f. = 0.853 (5)) coordination environment is formed by eight oxygen atoms with four pairs of equal contacts (d(Na2—O) = 2.4505 (16)–2.921 (2) Å, using a cut-off distance of 3.1 Å).
of (I) (Fig. 1). The basic building block of the structure is the [(Mn/Fe)2(PO4)3] unit, which consists of two (Mn/Fe)O6 polyhedra interlinked by three bridging PO4-tetrahedra (Fig. 2). These fragments alternate with Na1O6-polyhedra along [001] forming ribbons, which in turn are interconnected by PO4-tetrahedra forming a three-dimensional framework (Fig. 2). The distances M—O in the (Mn/Fe)O6 octahedra vary from 1.9962 (16) to 2.1053 (15) Å and are similar to that in isotypic structures (e.g. 1.956 (2)–2.048 (2) Å inFor applications and properties of NASICON-related compounds, see: Goodenough et al. (1976); Shimizu & Ushijima (2000); Veríssimo et al. (1997); Mariappan et al. (2005); Arbi et al. (2002); Moreno-Real et al. (2002). For details of structural relationships with other compounds, see: γ-Na3Fe2(PO4)3 (Masquelier et al., 2000); Na4Fe2(PO4)3 (Hatert, 2009); Na4MgFe(PO4)3 (Strutynska et al., 2012); Na4NiFe(PO4)3 (Essehli et al., 2011).
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell
CrysAlis CCD (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and enCIFer (Allen et al., 2004). ![]() | Fig. 1. The asymmetric unit of (I), showing displacement ellipsoids at the 50% probability level. |
![]() | Fig. 2. Elementary fragments and three-dimensional framework in the title compound. |
Na3.4Mn0.4Fe1.6(PO4)3 | Dx = 3.212 Mg m−3 |
Mr = 474.41 | Mo Kα radiation, λ = 0.71073 Å |
Trigonal, R3c | Cell parameters from 8867 reflections |
Hall symbol: -R 3 2" c | θ = 3.3–35.0° |
a = 8.8694 (2) Å | µ = 3.59 mm−1 |
c = 21.6074 (7) Å | T = 293 K |
V = 1472.05 (7) Å3 | Prism, light-violet |
Z = 6 | 0.10 × 0.10 × 0.08 mm |
F(000) = 1380 |
Oxford Diffraction Xcalibur-3 diffractometer | 728 independent reflections |
Radiation source: fine-focus sealed tube | 658 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.033 |
φ and ω scans | θmax = 35.0°, θmin = 3.3° |
Absorption correction: multi-scan (Blessing, 1995) | h = −14→14 |
Tmin = 0.721, Tmax = 0.795 | k = −13→14 |
8867 measured reflections | l = −34→34 |
Refinement on F2 | 2 restraints |
Least-squares matrix: full | Primary atom site location: structure-invariant direct methods |
R[F2 > 2σ(F2)] = 0.028 | Secondary atom site location: difference Fourier map |
wR(F2) = 0.072 | w = 1/[σ2(Fo2) + (0.0324P)2 + 3.4282P] where P = (Fo2 + 2Fc2)/3 |
S = 1.23 | (Δ/σ)max = 0.064 |
728 reflections | Δρmax = 0.66 e Å−3 |
38 parameters | Δρmin = −0.39 e Å−3 |
Na3.4Mn0.4Fe1.6(PO4)3 | Z = 6 |
Mr = 474.41 | Mo Kα radiation |
Trigonal, R3c | µ = 3.59 mm−1 |
a = 8.8694 (2) Å | T = 293 K |
c = 21.6074 (7) Å | 0.10 × 0.10 × 0.08 mm |
V = 1472.05 (7) Å3 |
Oxford Diffraction Xcalibur-3 diffractometer | 728 independent reflections |
Absorption correction: multi-scan (Blessing, 1995) | 658 reflections with I > 2σ(I) |
Tmin = 0.721, Tmax = 0.795 | Rint = 0.033 |
8867 measured reflections |
R[F2 > 2σ(F2)] = 0.028 | 38 parameters |
wR(F2) = 0.072 | 2 restraints |
S = 1.23 | Δρmax = 0.66 e Å−3 |
728 reflections | Δρmin = −0.39 e Å−3 |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Na1 | 0 | 0 | 0 | 0.0322 (8) | 0.848 (5) |
Na2 | 0.63677 (18) | 0 | 0.25 | 0.0356 (6) | 0.853 (5) |
Fe1 | 0 | 0 | 0.149480 (18) | 0.01045 (11) | 0.7991 (12) |
Mn1 | 0 | 0 | 0.149480 (18) | 0.01045 (11) | 0.2009 (12) |
P1 | 0.29637 (7) | 0 | 0.25 | 0.01144 (13) | |
O1 | 0.1887 (2) | −0.0197 (3) | 0.19242 (8) | 0.0346 (4) | |
O2 | 0.18883 (19) | 0.17055 (18) | 0.08615 (7) | 0.0214 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Na1 | 0.0421 (11) | 0.0421 (11) | 0.0124 (10) | 0.0211 (6) | 0 | 0 |
Na2 | 0.0206 (6) | 0.0151 (7) | 0.0694 (14) | 0.0075 (3) | 0.0068 (4) | 0.0136 (7) |
Fe1 | 0.01042 (13) | 0.01042 (13) | 0.01049 (17) | 0.00521 (7) | 0 | 0 |
Mn1 | 0.01042 (13) | 0.01042 (13) | 0.01049 (17) | 0.00521 (7) | 0 | 0 |
P1 | 0.01059 (19) | 0.0092 (2) | 0.0141 (2) | 0.00459 (12) | 0.00093 (9) | 0.00185 (18) |
O1 | 0.0270 (8) | 0.0404 (10) | 0.0327 (8) | 0.0142 (7) | −0.0155 (7) | 0.0016 (7) |
O2 | 0.0157 (6) | 0.0139 (6) | 0.0274 (7) | 0.0021 (5) | −0.0002 (5) | 0.0021 (5) |
Na1—O2i | 2.4546 (15) | Na2—O1x | 2.921 (2) |
Na1—O2 | 2.4546 (15) | Na2—O1xi | 2.921 (2) |
Na1—O2ii | 2.4546 (15) | Fe1—O1ii | 1.9962 (16) |
Na1—O2iii | 2.4546 (15) | Fe1—O1iii | 1.9962 (16) |
Na1—O2iv | 2.4546 (15) | Fe1—O1 | 1.9962 (16) |
Na1—O2v | 2.4546 (15) | Fe1—O2ii | 2.1053 (15) |
Na2—O2vi | 2.4505 (16) | Fe1—O2iii | 2.1053 (15) |
Na2—O2vii | 2.4505 (16) | Fe1—O2 | 2.1053 (15) |
Na2—O2viii | 2.472 (2) | P1—O1 | 1.5244 (16) |
Na2—O2ix | 2.472 (2) | P1—O1xii | 1.5244 (16) |
Na2—O1vii | 2.587 (2) | P1—O2ix | 1.5346 (15) |
Na2—O1vi | 2.587 (2) | P1—O2viii | 1.5346 (15) |
O2i—Na1—O2 | 180.00 (5) | O1vii—Na2—O1xi | 109.85 (7) |
O2i—Na1—O2ii | 111.27 (5) | O1vi—Na2—O1xi | 86.08 (4) |
O2—Na1—O2ii | 68.73 (5) | O1x—Na2—O1xi | 81.67 (9) |
O2i—Na1—O2iii | 111.27 (5) | O1ii—Fe1—O1iii | 100.14 (7) |
O2—Na1—O2iii | 68.73 (5) | O1ii—Fe1—O1 | 100.14 (7) |
O2ii—Na1—O2iii | 68.73 (5) | O1iii—Fe1—O1 | 100.14 (7) |
O2i—Na1—O2iv | 68.73 (5) | O1ii—Fe1—O2ii | 87.95 (7) |
O2—Na1—O2iv | 111.27 (5) | O1iii—Fe1—O2ii | 167.15 (7) |
O2ii—Na1—O2iv | 111.27 (5) | O1—Fe1—O2ii | 88.10 (7) |
O2iii—Na1—O2iv | 180.00 (8) | O1ii—Fe1—O2iii | 88.10 (7) |
O2i—Na1—O2v | 68.73 (5) | O1iii—Fe1—O2iii | 87.95 (7) |
O2—Na1—O2v | 111.27 (5) | O1—Fe1—O2iii | 167.15 (7) |
O2ii—Na1—O2v | 180.00 (9) | O2ii—Fe1—O2iii | 82.32 (6) |
O2iii—Na1—O2v | 111.27 (5) | O1ii—Fe1—O2 | 167.15 (7) |
O2iv—Na1—O2v | 68.73 (5) | O1iii—Fe1—O2 | 88.10 (7) |
O2vi—Na2—O2vii | 162.12 (10) | O1—Fe1—O2 | 87.95 (7) |
O2vi—Na2—O2viii | 129.35 (6) | O2ii—Fe1—O2 | 82.32 (6) |
O2vii—Na2—O2viii | 68.52 (7) | O2iii—Fe1—O2 | 82.32 (6) |
O2vi—Na2—O2ix | 68.52 (7) | O1—P1—O1xii | 110.62 (16) |
O2vii—Na2—O2ix | 129.35 (6) | O1—P1—O2ix | 112.19 (10) |
O2viii—Na2—O2ix | 60.85 (8) | O1xii—P1—O2ix | 106.30 (9) |
O2vi—Na2—O1vii | 114.64 (5) | O1—P1—O2viii | 106.30 (9) |
O2vii—Na2—O1vii | 68.83 (5) | O1xii—P1—O2viii | 112.19 (10) |
O2viii—Na2—O1vii | 68.62 (6) | O2ix—P1—O2viii | 109.33 (12) |
O2ix—Na2—O1vii | 93.19 (7) | P1—O1—Fe1 | 150.92 (13) |
O2vi—Na2—O1vi | 68.83 (5) | P1—O1—Na2xiii | 120.86 (11) |
O2vii—Na2—O1vi | 114.64 (5) | Fe1—O1—Na2xiii | 86.63 (6) |
O2viii—Na2—O1vi | 93.19 (7) | P1—O1—Na2xiv | 76.78 (7) |
O2ix—Na2—O1vi | 68.62 (6) | Fe1—O1—Na2xiv | 102.77 (7) |
O1vii—Na2—O1vi | 159.36 (11) | Na2xiii—O1—Na2xiv | 112.45 (8) |
O2vi—Na2—O1x | 53.35 (5) | P1ix—O2—Fe1 | 141.73 (9) |
O2vii—Na2—O1x | 111.21 (7) | P1ix—O2—Na2xiii | 93.51 (8) |
O2viii—Na2—O1x | 153.24 (6) | Fe1—O2—Na2xiii | 87.96 (6) |
O2ix—Na2—O1x | 114.32 (5) | P1ix—O2—Na1 | 128.40 (8) |
O1vii—Na2—O1x | 86.07 (4) | Fe1—O2—Na1 | 89.86 (5) |
O1vi—Na2—O1x | 109.85 (7) | Na2xiii—O2—Na1 | 86.38 (5) |
O2vi—Na2—O1xi | 111.22 (7) | P1ix—O2—Na2ix | 94.91 (7) |
O2vii—Na2—O1xi | 53.35 (5) | Fe1—O2—Na2ix | 87.39 (6) |
O2viii—Na2—O1xi | 114.32 (5) | Na2xiii—O2—Na2ix | 171.00 (7) |
O2ix—Na2—O1xi | 153.24 (6) | Na1—O2—Na2ix | 85.91 (5) |
Symmetry codes: (i) −x, −y, −z; (ii) −x+y, −x, z; (iii) −y, x−y, z; (iv) y, −x+y, −z; (v) x−y, x, −z; (vi) y+2/3, −x+y+1/3, −z+1/3; (vii) x+1/3, x−y−1/3, z+1/6; (viii) −x+y+1/3, y−1/3, z+1/6; (ix) −x+2/3, −y+1/3, −z+1/3; (x) y+1, x, −z+1/2; (xi) −x+y+1, −x, z; (xii) x−y, −y, −z+1/2; (xiii) x−y−1/3, x−2/3, −z+1/3; (xiv) −y, x−y−1, z. |
Experimental details
Crystal data | |
Chemical formula | Na3.4Mn0.4Fe1.6(PO4)3 |
Mr | 474.41 |
Crystal system, space group | Trigonal, R3c |
Temperature (K) | 293 |
a, c (Å) | 8.8694 (2), 21.6074 (7) |
V (Å3) | 1472.05 (7) |
Z | 6 |
Radiation type | Mo Kα |
µ (mm−1) | 3.59 |
Crystal size (mm) | 0.10 × 0.10 × 0.08 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur-3 |
Absorption correction | Multi-scan (Blessing, 1995) |
Tmin, Tmax | 0.721, 0.795 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8867, 728, 658 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.807 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.072, 1.23 |
No. of reflections | 728 |
No. of parameters | 38 |
No. of restraints | 2 |
Δρmax, Δρmin (e Å−3) | 0.66, −0.39 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 1999), WinGX (Farrugia, 1999) and enCIFer (Allen et al., 2004).
Na1—O2 | 2.4546 (15) | Fe1—O1 | 1.9962 (16) |
Na2—O2i | 2.4505 (16) | Fe1—O2 | 2.1053 (15) |
Na2—O2ii | 2.472 (2) | P1—O1 | 1.5244 (16) |
Na2—O1i | 2.587 (2) | P1—O2ii | 1.5346 (15) |
Na2—O1iii | 2.921 (2) |
Symmetry codes: (i) y+2/3, −x+y+1/3, −z+1/3; (ii) −x+y+1/3, y−1/3, z+1/6; (iii) y+1, x, −z+1/2. |
Acknowledgements
The authors are grateful to Dr. Igor V. Zatovsky from Department of Inorganic Chemistry, Taras Shevchenko National University, Kiev, Ukraine, for valuable comments and support.
References
Allen, F. H., Johnson, O., Shields, G. P., Smith, B. R. & Towler, M. (2004). J. Appl. Cryst. 37, 335–338. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Arbi, K., Mandal, S., Rojo, J. M. & Sanz, J. (2002). Chem. Mater. 14, 1091–1097. Web of Science CrossRef CAS Google Scholar
Blessing, R. H. (1995). Acta Cryst. A51, 33–38. CrossRef CAS Web of Science IUCr Journals Google Scholar
Brandenburg, K. (1999). DIAMOND. University of Bonn, Germany. Google Scholar
Essehli, R., Bali, B. E., Benmokhtar, S., Bouziane, K., Manoun, B., Abdalslam, M. A. & Ehrenberg, H. (2011). J. Alloys Compd, 509, 1163–1171. Web of Science CrossRef CAS Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Goodenough, J. B., Hong, H. Y. P. & Kafalas, J. A. (1976). Mater. Res. Bull. 11, 203–220. CrossRef CAS Web of Science Google Scholar
Hatert, F. (2009). Acta Cryst. E65, i30. Web of Science CrossRef IUCr Journals Google Scholar
Mariappan, C. R., Govindaraj, G. & Roling, B. (2005). Solid State Ionics, 176, 723–729. Web of Science CrossRef CAS Google Scholar
Masquelier, C., Wurm, C., Rodríguez-Carvajal, J., Gaubicher, J. & Nazar, L. (2000). Chem. Mater. 12, 525–532. Web of Science CrossRef CAS Google Scholar
Moreno-Real, L., Maldonado-Manso, P., Leon-Reina, L., Losilla, E. R., Mouahid, F. E., Zahir, M. & Sanz, J. (2002). J. Mater. Chem. 12, 3681–3687. CAS Google Scholar
Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Shimizu, Y. & Ushijima, T. (2000). Solid State Ionics, 132, 143–148. Web of Science CrossRef CAS Google Scholar
Strutynska, N. Yu., Zatovsky, I. V., Yatskin, M. M., Slobodyanik, N. S. & Ogorodnyk, I. V. (2012). Inorg. Mater. 48, 402–406. Web of Science CrossRef CAS Google Scholar
Veríssimo, C., Garrido, F. M. S., Alves, O. L., Calle, P., Martínez-Juárezc, A., Iglesias, J. E. & Rojo, J. M. (1997). Solid State Ionics, 100, 127–134. Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
NASICON-type compounds possess high ionic conductivity, chemical stability and attract great interest for application in solid-state electrochemical devices (Goodenough et al., 1976; Shimizu & Ushijima, 2000; Veríssimo et al., 1997; Mariappan et al., 2005; Arbi et al., 2002; Moreno-Real et al., 2002).
Herein, the structure of Na3.4Mn0.4Fe1.6(PO4)3, (I), is reported. Compound (I) can be considered as a solid solution of γ-Na3Fe2(PO4)3 (Masquelier et al., 2000) and belongs to the NASICON structure type.
There are two Na sites (Wyckoff positions 6b and 18e), one mixed occupied Mn/Fe site (12c), one P site (18e) and two O sites (36f) in the asymmetric unit of (I) (Fig. 1). The basic building block of the structure is the [(Mn/Fe)2(PO4)3] unit, which consists of two (Mn/Fe)O6 polyhedra interlinked by three bridging PO4-tetrahedra (Fig. 2). These fragments alternate with Na1O6-polyhedra along [001] forming ribbons, which in turn are interconnected by PO4-tetrahedra forming a three-dimensional framework (Fig. 2). The distances M—O in the (Mn/Fe)O6 octahedra vary from 1.9962 (16) to 2.1053 (15) Å and are similar to that in isotypic structures (e.g. 1.956 (2)–2.048 (2) Å in γ-Na3Fe2(PO4)3 (Masquelier et al., 2000); 2.010 (6)–2.130 (6) Å in Na4Fe2(PO4)3 (Hatert, 2009); 1.926 (5)–2.037 (6) Å in Na4MgFe(PO4)3 (Strutynska et al., 2012); 1.955 (3)–2.050 (3) Å in Na4NiFe(PO4)3 (Essehli et al., 2011). The P atom has an almost regular tetrahedral coordination, the P—O distances in the PO4 tetrahedra being in the range 1.5244 (16)–1.5346 (15) Å, as is typically observed in NASICON-type phosphates. Two types of sodium atoms occupy the cavities of the framework. The Na1 atoms (s.o.f. = 0.848 (5)) lie on a threefold roto-inversion axis and are surrounded by six O2 atoms in a distance of 2.4546 (15) Å. The Na2 (s.o.f. = 0.853 (5)) coordination environment is formed by eight oxygen atoms with four pairs of equal contacts (d(Na2—O) = 2.4505 (16)–2.921 (2) Å, using a cut-off distance of 3.1 Å).