SYNTHESIS AND STRUCTURE OF BA6HF5S16 AND BA5HF4S13 - THE N = 5 AND 4 MEMBERS OF THE AN+1BNX3N+1 RUDDLESDEN-POPPER PHASES

Two new Ba/Hf/S phases of formula Ba5Hf4S13 and Ba6Hf5S16 have been prepared from BaS, Hf, and elemental sulfur at 1050-degrees-C in BaCl2 flux reactions. The compounds are the n = 4 and 5 members of the Ban+1HfnS3n+1 series which are rare examples of Ruddlesden-Popper sulfides. The compounds contain perovskite blocks extending infinitely in a and b with double BaS layers and a 0 1/2 0 shift every n layers in c. The Hf-S distances in both compounds average 2.48 (2) angstrom with regular HfS6 octahedra. The 12-coordinate Ba atoms display Ba-S distances averaging 3.49 (2) angstrom with the Ba-S distances for the 9-coordinate Ba atoms in the double BaS layers ranging between 3.08 and 3.52 angstrom. Crystal data for Ba5Hf4S13 (20-degrees-C): a = 6.977 (1) angstrom, b = 7.006 (2) angstrom, and c = 45.280 (5) angstrom, Z = 4, D(calc) = 5.45 g/cm3, orthorhombic, space group Fmmm. Crystal data for Ba6Hf5S16 (20-degrees-C): a = 7.002 (1) angstrom, b = 6.987 (2) angstrom, and c = 55.205 (6) angstrom, z = 4, D(calc) = 5.48 g/cm3, orthorhombic, space group Fmmm.