CdZn2KB2O6F, a new fluoride borate crystal.

During an attempt to grow crystals of the nonlinear optical material Cd(3)Zn(3)B(4)O(12) using a KBF(4) flux, crystals of a new cadmium dizinc potassium borate fluoride compound, CdZn(2)KB(2)O(6)F, were unexpectedly isolated. The structure consists of layers constructed of distorted corner-sharing ZnO(3)F tetrahedra and BO(3) triangles. Both Zn and B reside on threefold rotation axes, while the F(-) anion is located at a site of 3.2 symmetry. The Cd(II) (site symmetry 3) and K(+) (site symmetry 3.2) ions occupy six- and nine-coordinate interlayer sites, respectively. The BO(3) triangles and ZnO(3) pyramids from the ZnO(3)F tetrahedra share bridging O atoms with each other to form an extended [ZnBO(3)] layer parallel to (001). Although these layers are similar to the [MBO(3)] layers seen in other compounds, they are uniquely bridged here by the Cd centres and F(-) anions to form a three-dimensional framework. In so doing, a series of channels is formed along the [010] direction and the K(+) cations are found in these channels.