A new Nasicon phosphates series [Na3+xCr2–xCox(PO4)3(0<=x<=1)] was synthesized by a coprecipitation method and structurally characterized by powder X-ray diffraction. The selected compound Na3.5Cr1.5Co0.5(PO4)3 (x=0.5) crystallizes in the R[overline 3]c space group with the following hexagonal unit-cell dimensions: ah=8.7285(3) Å, ch=21.580(2) Å, V=1423.8(1) Å3, and Z=6. This three-dimensional framework is built of PO4 tetrahedra and Cr/CoO6 octahedra sharing corners. Na atoms occupy totally M(1) sites and partially M(2) sites.
