Crystal structure of calcium dinickel(II) iron(III) tris(orthophosphate): CaNi₂Fe(PO₄)₃

Abstract

The transition metal orthophosphate CaNi2Fe(PO4)3 adopts the α-CrPO4 structure type. The structure is built up from two types of sheets, resulting in an open three-dimensional framework that delimits two types of channels in which the CaII cations are located.

Topological Features of the Alluaudite-Type Framework and Its Derivatives: Synthesis and Crystal Structure of NaMnNi2(H2/3PO4)3

“…Because of the wide isomorphism in the cationic and anionic parts of the alluaudite-type structures, they attract interest as advanced materials for Li-ion batteries [22][23][24][25][26][27][28]. Despite the observed chemical diversity, Ni-containing alluaudite-type compounds are represented only by anhydrous phosphates Na 2 MNi 2 (PO 4 ) 3 (M = Fe, Al) [29,30] and CaFeNi 2 (PO 4 ) 3 [31], mixed phosphate-hydrogen phosphate AgNi 3 (PO 4 )(HPO 4 ) 2 [32], sulfate Na 2 Ni 2 (SO 4 ) 3 [33,34], and mixed sulfate-selenate Na 3 Ni 1.5 (SO 4 ) 3-1.5x (SeO 4 ) 1.5x [35].…”

Crystal structure of barium dinickel(II) iron(III) tris[orthophosphate(V)], BaNi2Fe(PO4)3

“…The title compound is related to the strontium and calcium homologs MNi 2 Fe(PO 4 ) 3 (M = Sr, Ca; Ouaatta et al, 2015Ouaatta et al, , 2017, all adopting the -CrPO 4 structure type (Attfield et al, 1986). The asymmetric unit of BaNi 2 Fe(PO 4 ) 3 is comprised of ten sites, eight of which are on special positions, except the O3 and O4 sites on a general position (Wyckoff position 16 j).…”

“…The formula of -CrPO 4 can be written as X1X2Cr1Cr2 2 (PO 4 ) 3 , where X1, X2 represent the empty channel sites. Accordingly, the substitution of Cr1 or Cr2 by a divalent cation requires charge compensation by cations located in the channels to result in AA'MM' 2 (PO 4 ) 3 compounds such as BaNi 2 Fe(PO 4 ) 3 , or MNi 2 Fe(PO 4 ) 3 (M = Sr, Ca; Ouaatta et al, 2015Ouaatta et al, , 2017. The difference between BaNi 2 Fe(PO 4 ) 3 and the closely related MNi 2 Fe(PO 4 ) 3 structures pertains to the M site, which is split into two sites for the title compound and fully occupied for M = Ca, Sr.…”

“…Crystal data, data collection and structure refinement details are summarized in Table 3. After assignment of the atomic sites according to the related MNi 2 Fe(PO 4 ) 3 structures (M = Sr, Ca; Ouaatta et al, 2015Ouaatta et al, , 2017, a difference-Fourier map revealed a maximum electron density of 3.61 A ˚À3 that was finally modeled as a considerably underoccupied Ba site (Ba2). For the final model, the sum of site-occupation factors for the Ba1 and Ba2 sites were constrained to be 1.…”

Structural and Spectroscopic Studies of NaCuCr2(PO4)3: A Noncentrosymmetric Phosphate Belonging to the α-CrPO4-Type Compounds

“…They are identified with the general chemical formula □ 3 M 3 (XO 4 ) 3 , where □ is a vacancy that can be filled by monovalent and/or divalent cations, introducing an oxidation state decrease of the transition metal M and XO 4 referring to tetrahedral entity, respectively. They all crystallize with a centrosymmetric Imma space group. − Interestingly, some of them with the following general formula A 2 M 2+ 2 M 3+ (PO 4 ) 3 , where A is an alkali and M are metals able to show an oxidation equal to 2 and/or 3, were recently described as low-temperature polymorphs of the alluaudite-type structure. , …”