Synthesis and crystallochemistry of Na4CrNi(PO4)3

Na4CrNi(PO4)(3) orthophosphate powder was prepared from acid solutions of NiO, Na2CO3 and aqueous solutions of Cr(NO3)(3).9H(2)O, and (NH4)(2)HPO4 at a final temperature of 750degreesC. The hexagonal unit cell parameters were determined to be a(h) approximate to 8.789 Angstrom and C-h approximate to 21.481 Angstrom in space group R (3) over barc. These parameters were compared to those of Na(4)AA'(PO4)(3) (AA' = CrMg, CrCo, TiNa, ZrNa). The linear variations of these parameters versus the mean A cation radius (r(AA')) are consistent with the atomic distribution found for the structure of Na4NiCr(PO4)(3). The a(h) and C-h parameters are functions of the A(n+) ion size. (C) 2004 Intemational Centre for Diffraction Data.