Crystal structure of chain silicate Cs 3 LuSi 3 O 9 .

A caesium lutetium(III) silicate, Cs 3 LuSi 3 O 9 , was synthesized by heating a pelletized mixture of Cs 2 CO 3 , Lu 2 O 3 and SiO 2 at 1273 K. Single crystals of the title compound were grown in a melted area of the pellet. Cs 3 LuSi 3 O 9 is a single-chain silicate (ortho-rhom-bic space group Pna 2 1 ) with a chain periodicity of six and is isostructural with Cs 3 RE III Ge 3 O 9 ( RE = Pr, Nd and Sm-Yb). The two symmetry-dependent [Si 6 O 18 ] 12- chains in the unit cell lie parallel to the [011] direction. The Lu 3+ ions are octa-hedrally coordinated by O atoms of the silicate chains, generating a three-dimensional framework. Cs + ions are located in the voids in the framework.