A NEW-TYPE OF MIXED ANIONIC FRAMEWORK IN THE STRUCTURE OF K-3[AL4F9(PO4)(2)]

X-ray analysis of a hydrothermally synthesized potassium aluminium flu oride orthophosphate, K-3[Al4F9-(PO4)(2)]. showed that this compound h as a new type of crystal structure. Three kinds of cis-AlF4O2 octahedr a share common vertices to form branched [Al4F9O8](n) chains parallel to the a axis of the monoclinic unit cell. In the b and c directions t hese chains are linked by PO4 tetrahedra to give a three-dimensional f ramework of octahedra and tetrahedra. The open structure exhibits seve ral crossed channels suggesting possible cationic transport properties . The two largest of these channels are occupied by the K+ cations.