Pb_3Mn_5V_2O_(16): a new lead manganese vanadate with double Mn~(II)/Mn~(IV) valence

摘要

A new lead manganese vanadium oxide was prepared and analyzed by single crystal X-ray diffraction, a=5.754(2), c=11.475(5) A, space group P3m1, R_1=0.02, wR_2=0.04. The crystal structure shows evidence of a double II and IV manganese valence discriminated on two independent crystallographic sites. Its crystal structure results from a (B'ABA') type close-packing of PbO_3 and O_4 layers. The resulting blocks are surrounded by PbO_2 layers. Thus, the available interstices occupancy leads to the creation of a Kagome lattice of Mn~(IV)O_6 octahedra. At the upper layer, the Kagome windows are occluded by Mn~(II)O_6 octahedra via J_(K/O) junctions. These octahedral pillars share their corners with a double layer formed of isolated V~VO_4 tetrahedra. The polyhedra linkage leads to an original crystal structure that is compared to several materials such as spinels and related compounds. Efforts provided to prepare the title compound and isostructural materials are also mentioned in this work.