Chromium-containing NASICON-related phosphates of the type Na(1+x)CrxM(2-x)P3O12 (M=Ti, Hf, Zr) have been synthesised by solid state reaction and structurally characterised by Rietveld refinement of the powder X-ray diffraction data. Materials of composition A((1+x)/2)Cr(x)Zr((2-x)) P3O12 (A=Cd, Ca, Sr), have also been prepared and characterised. The crystal structure of Na(1+x)CrxM(2-x)P3O12 corresponds to R-3c symmetry for x values ranging from 0.15 to 2.00, whereas compounds of composition A((1+x)/2)Cr(x)Zr((2-x))P(3)O(12) corresponding to R-3c are obtained when x <= 1.00 for St(2+) and Ca2+, and x <= 1.50 for Cd2+. The polarizing effect of the two different metal ions A and M on the phosphorus atom and the P-O bond was studied by both P-31 MAS NMR and infrared spectroscopy and shows that the electron density on the phosphorus, and thus the strength of the P-O bonds, are affected by both the interstitial (A) and the structural (M) metal ions. (c) 2006 Elsevier B.V. All rights reserved.