Crystal structure determination of the oxynitride Sr2TaO3N

The crystal structure of the strontium tantalum oxynitride Sr2TaO3N has bee n resolved by Rietveld refinement using time-of-flight neutron powder diffr action data. The structure is of the K2NiF4 type with a partially ordered a nion sublattice (tetragonal, I4/mmm, a = 4.04127(3) Angstrom, c = 12.6073(2 ) Angstrom, c/a = 3.120, Z = 2), The tantalum atoms are at the center of Ta O2(O, N)(4) octahedra built up from two oxygen atoms at the apexes and four (N + O) atoms statistically forming the median plane, The strontium atoms have a coordination number of nine: SrO5(O, N)(4). The profile agreement fa ctors are R-p = 0.022, R-wp = 0.016, R-exp = 0.012, and R-I = 0.063. (C) 19 99 Academic Press.