Synthesis and investigation of novel Mn-based oxyfluoride Sr_2Mn_2O_(5-x)F_(1+x)

摘要

A new oxyfluoride Sr_2Mn_2O_(5-x)F_(1+x) was synthesized by low temperature fluorination of Sr_2Mn_2O_5 with XeF_2 and studied using X-ray powder diffraction, electron diffraction and high resolution electron microscopy. The oxyfluoride has a tetragonal perovskite-like structure with cell parameters a = 3.8069(8) A, c = 3.989(2) A (S.G. P4/mmm). No additional superstructure or lattice distortions were detected by electron microscopy. The Mn oxidation state was evaluated using bond valence sum calculations as close to V_(Mn) = +3.5. The tetragonal distortion of the perovskite structure arises from the Jahn-Teller deformation of the Mn(O, F)_6 octahedra.