Structure determination of Al0.67Fe0.33PO4:: An example of convergence of X-ray diffraction and Mossbauer spectroscopy results

The composition Al0.67Fe0.33PO4 along the join AlPO4 - FePO4 was prepared with a non conventional sor-gel method The sample was characterized by X-ray powder diffraction (XRPD) and by Mossbauer spectroscopy (MS) on (57) Fe, at room temperature. The X-ray powder pattern, atomic coordinates and thermal parameters are reported together with the Isomeric Shift and Quadrupole Splitting. No significant difference between the structural resultances of XRDP and MS spectroscopies was evidenced. These methods therefore are mutually supporting; moreover the X-ray evidence, which averages on the dimensional characteristics of AlO4 and FeO4 tetrahedra, as Fe and Al are mutually substituting on the same atomic position, is in agreement with Mossbauer spectroscopy data which on the contrary, depend only on the FeO4 tetrahedra, One can therefore infer that the AlO4 tetrahedra are here structurally similar to FeO4 tetrahedra.