Our ability to design new materials with desired electrochemical, thermoelectric or strongly-correlated electron properties is limited by thermodynamic control over reaction products in traditional high-temperature synthetic procedures. On the contrary, topotactic reactions, where extensive parts of the original framework are retained, allow for greater control of the structure of the final products; therefore, a combination of desired structural features, spin and oxidation states can be produced in a final material in a predictable fashion.In all known compounds with the alpha-NaFeO2 structure transition metals oxidation states are either 3+ or 3+/4+. We have developed an �aliovalent exchange plus intercalation� multistep soft chemistry approach for the preparation of a series of new layered transition metal oxides. The synthetic procedure resulted in compounds with the alpha-NaFeO2 type structures and, uniquely, with transition metals in mixed valent 2+/3+ oxidation states. The oxidation state in the final compounds can be controlled by utilizing AxMO2 precursor phase with different x. Crystal structures and physical properties of these novel compounds will be presented.Compounds with the alpha-NaFeO2 structure are generally not considered part of a homologue series; however, one can imagine rock-salt related structures with layered ordering of alkali and d metal cation ratios of 1 to 2, 1 to 3 and so on; thus establishing a new AMnOn+1 (A = alkali metal, M = d metal) rock-salt related homologue series with layered cation ordering. Beta-NaFe2O3 is a n = 2 member of the homologue series. Physical properties of beta-Na1-xFe2O3 will be presented and compared with alpha-NaFeO2 and isoelectronic Na1-xCoO2.

Multistep topotactic route to novel strongly correlated-electron materials with rock-salt related structures

246th National Meeting (2013)

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