Crystal Structures and Ionic Conductivities of Ternary Derivatives of the Silver and Copper Monohalides: I. Superionic Phases of Stoichiometry MA4I5:RbAg4I5, KAg4I5, and KCu4I5

A second lanthanum ruthenium oxide with the formula La3RuO7 is reported. This compound, BETA-La3RuO7, crystallizes in the P21/c space group with a unit cell of a=8.8388(3) ?, b=5.6960(1) ?, c=12.5830(3) ?, and BETA=104.729(1) °, as refined from powder neutron diffraction data. The two major structural motifs in this structure are isolated RuO6 octahedra and edgesharing chains of OLa4 tetrahedra. Magnetic susceptibility measurements show this compound to have a magnetic moment of MUeff=3.92MU and a Weiss constant of =-70 K.