Topochemical Cation Exchange Reactions of Na2MnTeO6

Na₂MnTeO₆ adopts a structure comprising layers of edge-sharing MnO₆ and TeO₆ octahedra, separated by interlayer Na⁺ cations. By reacting the ‘parent’ phase Na₂MnTeO₆, with binary metal chlorides (NiCl2, CuCl2 and ZnCl2) the exchanged phases ‘NiMnTeO₆’, ‘ZnMnTeO₆’, and ‘CuMnTeO₆’ can be produced in which the sodium cations in the parent phase have been replaced by transition metal cations. However, while chemical titrations indicate Na2MnTeO6 contains Mn4+, the cation-exchanged materials appear to contain Mn3+, suggesting the exchanged phases actually have compositions of M1.5MnTeO6 (M = Ni, Cu, Zn) and that a redox reaction has occurred during the cation exchange. We propose to collect neutron powder diffraction data at room temperature from these phases to accurately determine their crystal structures, specifically the locations of the exchanged cations, and any local orbital ordering of the Mn3+ Jahn-Teller distortion. We also propose to collect diffraction data at low temperature to study the magnetic ordering of ‘NiMnTeO₆’ and ‘CuMnTeO₆’.