Crystal Structure Determination of the Oxynitride Sr2TaO3N

The crystal structure of the strontium tantalum oxynitride Sr2TaO3N has been resolved by Rietveld refinement using time-offlight neutron powder diffraction data. The structure is of the K2NiF4 type with a partially ordered anion sublattice (tetragonal, I4/mmm, a=4.04127(3) ?, c=12.6073(2) ?, c/a=3.120, Z=2). The tantalum atoms are at the center of TaO2(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 factors are Rp=0.022, Rwp=0.016, Rexp=0.012, and RI=0.063.