Ag13I4(AsO4)3: Synthesis, Crystal Structure and Ionic Conductivity

Ruby-red single crystals of Ag13I4(ASO(4))(3) were prepared for the first time by reacting a stoichiometric mixture of Ag2O, AgI and As2O3 at elevated oxygen pressure of 120 MPa and at a temperature of 350 degrees C. The polyhedral crystals belong to the monoclinic space group P2(1)/m with a = 9.247(1), b = 7.152(1), c = 17.674(2) angstrom, beta = 91.492(2)degrees, and Z = 2. The structure is fully ordered and was solved by Direct Methods, and refined on single crystal diffraction data (10376 observed reflections, R1 = 3.28%). The crystal Structure is built up of two two-dimensional interlocked partial Structures, one consisting of silver and iodine ions. the other of silver and arsenate(V) ions. The slabs extend in the ac plane, and the Ag-I framework is linked to the AsO43- units by Ag-O contacts. The silver-oxygen interactions perturb the tetrahedron of the arsenate group, resulting in As-O distances ranging from 1.670 to 1.697 angstrom, and angles varying from 107.3 to 112.1 degrees. Pure Ag13I4(AsO4)(3) is a solid ion conductor with a r.t. conductivity of 6.4 x 10(-6) Omega(-1) cm(-1) at 30 degrees C. The activation energy for silver ion conduction is 0.41 eV in the temperature range from 30 to 130 degrees C.