Characterization of Mn 7SiO 12, a synthetic equivalent of “braunite” a natural mineral with various manganese sites

Abstract

A redox reaction between Mn 2+Cl 2, Mn 4+O 2 and SiO 2 occurs above 600 °C, in sealed tubes, giving a new compound: Mn 7SiO 12. Crystals have a tetragonal symmetry, space group I4 1 acd , with a = 9.371(2) A ̊ , c = 18.847(8) A ̊ , Z = 8. A full structural determination has been realized. Crystallographic data show that Mn 7SiO 12 is isomorphic to “Braunite”, a natural mineral. Manganese atoms exist at two oxydation states (2 + and 3 +) and present cubic (Mn 2+) and octahedral (Mn 3+) coordinations. Preliminary magnetic and infrared characterizations have been performed.