High pressure synthesis of NaMn7O12: structural characterizaztion and P/T stability

This work presents a study on the synthesis and P/T phase diagram of NaMn7O12. It crystallizes in a perovskite structure; the presence of a double valence Mn in the B-site of the perovskite, gives rise to a series of interesting characteristics, including structural transitions (due to Jahn-Teller distorsions of the Mn3+O6 octahedra) and magnetic ones (due to charge and orbital ordering phenomena). NaMn7O12 is synthesized under high pressure in a multi-anvil apparatus at IMEM-CNR. A number of synthesis have been carried out to define its stability region of in the P-T plot. The structure, determined by powder and single-crystal X-rays and neutron diffraction, belongs to the cubic Im3 space group with a = 7.312 Å and Z = 2. The effects of the precursors and of the Na content on the product purity are also reported.