JOURNAL of the Tunisian Chemical Society

The trisodium yttrium-aluminum triarsenic dodecaoxide Na₃Y_0,11Al_1.89(AsO₄)₃, synthesized by solid-state method and characterized by single-crystal X-ray diffraction, crystallizes in the rhombohedral system, space group R3c . The parameters of the hexagonal cell are a = 13.354(1) Å; c = 18.335(3) Å and Z = 12. The structure was determined using 538 independent reflections and refined until (R(F) = 0,038; wR(F²) = 0.109). It is built of a three-dimensional framework [Y_0.22Al_3,78(AsO₄)₆]_n^6n- into which the sodium cations Na⁺ are inserted. The framework is made up of Al₄O₁₈ clusters( three Al(2) octahedra sharing an edge with a central octahedron Al(1)) and YO₆ octahedra linked to AsO₄ tetrahedra. Each tetrahedron shares two oxygen atoms, O(2) and O(3), with a first cluster Al₄O₁₈ and one oxygen atom, O(1), with a second cluster, the fourth oxygen atom, O(4), is connected to the Y(O(4))6 octahedron. The structure of this compound is compared with the Nasicon-type phosphates Na₃M₂(PO₄)₃. The impedance spectroscopy measurements were used to evaluate the variation of electrical properties, vs the doped rate by Na₂O, of this material.

W. Belam, A. Madani, A. Driss, A. Daoud

Pages 735-743