Synthesis, structure and conductivity study of new monovalent phosphates with the langbeinite structure

This paper reports the synthesis, structure and the conductivity study of the new monovalent phosphates of the formula Na2MTi(PO4)3, M=Fe or Cr. The structures of these compounds have been refined from X-ray powder diffraction by the Rietveld method. Their reflections are indexed in the cubic system with langbeinite-type structure in the P213 space group. This structure can be best described in terms of [M2P3O18] structural units composed of two MO6 octahedra linked to each other through three PO4 tetrahedra. Curie-type behaviour is observed in the magnetic susceptibility, which confirms the trivalent state of M metals and suggest no magnetic interactions. The electrical behaviour of these phases show that the activation energies are relatively high and they could be related to the previous structural analysis