K(9)Y(3)[Si(12)O(32)]F(2)

Single-crystals of the title compound, nona­potassium triyttrium dodeca­silicate difluoride, were obtained from flux synthesis experiments in the system SiO(2)—Y(2)O(3)—KF. The crystal structure belongs to the group of single-layer silicates and is based on silicate sheets parallel to (110). A single layer contains secondary (Q (2)) and tertiary (Q (3)) silicate tetra­hedra in the ratio 1:2 and is build up from six-, eight- and twelve-membered rings. The linkage between neighboring layers is achieved by two crystallographically independent Y(3+) cations, which are coordinated by six oxygen ligands in form of distorted octa­hedra. Charge compensation is accomplished by incorporation of additional F(−) anions and K(+) cations in the structural channels, forming anion-centred [F(2)K(7)] groups. Apart from one K(+) and one Y(3+) cation (each with site symmetry -1), the 30 crystallographically independent atoms reside on general positions.