A Cubic Non-Centrosymmetric Mixed-Valence Iron Borophosphate-Phosphite

A first member of a new family of metal borophosphate-phosphite Fe(1.834)(II)Fe(0.166)(III)B0.5[PO3(OH)](0.8)-(HPO3)(2.033) has been successfully synthesized by using the boric acid-phosphorous acid flux. The compound crystallizes in the cubic crystal System in a non-centrosymmetric space group I (4) over bar 3d (No. 220) with unit cell parameters of a = 21.261(3) angstrom, and Z = 48, featuring a very condensed network of FeO6 octahedra and disordered phosphate-phosphite moieties with mixed valency of iron. The compound contains a novel fundamental building unit (FBU), a cyclic borophosphate-phosphite ring which is further connected to forma propeller like partial anionic structure. Metal polyhedra also form a propeller like structure through edge-sharing and are further connected to the partial anionic structure to form the three-dimensional structure. Thermal analyses, infrared and Mossbauer spectroscopy, magnetic and second harmonic generating (SHG) measurements using 1064 urn radiation have been performed on this compound. SHG-measurements indicate that the compound has an efficiency approximately equal to alpha-SiO2.