A NEW FLUOROPHOSPHATE WITH A LAUEITE-TYPE STRUCTURAL UNIT - SYNTHESIS, TEM STUDY AND CRYSTAL-STRUCTURE OF SRFEPO4F2

SrFePO4F2 was synthesized by hydrothermal growth (700 degrees C, 180MP a, 24h). The crystal structure [space group P2(1)/n, a = 5.207(1)Angst rom, b = 12.216(1)Angstrom, c = 7.037(1)Angstrom, beta = 103.00(2)degr ees, Z = 4] was refined from single crystal X-Ray data to R-1=0.039 (o mega R-2=0.108) for 1774 independent reflections. Selected Area Electr on Diffraction (SAED) and High Resolution Electron Microscopy (HREM) c onfirmed the structure. The structure consists of FeO2F4, FeO4F2 and P O4 polyhedra linked in order to form a two-dimensional framework betwe en which the Sr2+ cations are inserted. The FePO4F2 sheet is topologic ally identical to the structural unit of the mineral laueite; structur al relationships are presented in this paper.