SYNTHESIS AND STRUCTURE OF CS3TI3AS5O20

A new ternary titanium arsenate, Cs3Ti3As5O20, has been synthesized an d structurally characterized by single-crystal X-ray diffraction. It c rystallizes in the orthorhombic space group Pbcm (no. 57) with a = 6.5 084(9), b = 19.167(l ), c = 1 5.377(l) angstrom, Z = 4 and R = 0.0259. The structure consists of tunnels where the caesium cations are locat ed. The framework is formed by corner-sharing monomeric TiO6 octahedra , dimeric Ti2O11 units consisting of two corner-sharing TiO6 octahedra , AsO4 tetrahedra, and As2O7 groups. The structural formula is Cs3Ti(T i2O) (AsO4)3(AS2O7). The structure is compared with that of alpha-CsTi 3P5O19.