Issue 4, 2021

Structural modulation in potassium birnessite single crystals


We report on the growth of single-crystal potassium birnessite (K0.31MnO2·0.41H2O) and present both the average and local structural characterization of this frustrated magnetic system. Single crystals were obtained employing a flux growth method with a KNO3/B2O3 flux at 700 °C. Single-crystal X-ray diffraction revealed an average orthorhombic symmetry, with space group Cmcm. A combination of high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with atomic resolution energy dispersive X-ray spectroscopy (EDS) demonstrated the layered structure of potassium birnessite with manganese-containing planes well separated by layers of potassium atoms. MnO6 octahedra and the K/H2O planes were clearly imaged via integrated differential phase contrast (iDPC) STEM. Furthermore, iDPC-STEM also revealed the existence of local domains with alternating contrast of the manganese oxide planes, most likely originating from charge ordering of Mn3+ and Mn4+ along the c-axis. These charge-ordered domains are clearly correlated with a reduction in the c-lattice parameter compared to the rest of the matrix. The insight gained from this work allows for a better understanding of the correlation between structure and magnetic properties.

Graphical abstract: Structural modulation in potassium birnessite single crystals

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Article information

Article type
17 Nov 2020
20 Dec 2020
First published
21 Dec 2020
This article is Open Access
Creative Commons BY license

J. Mater. Chem. C, 2021,9, 1370-1377

Structural modulation in potassium birnessite single crystals

L. D. Kulish, P. Nukala, R. Scholtens, A. G. M. Uiterwijk, R. Hamming-Green and G. R. Blake, J. Mater. Chem. C, 2021, 9, 1370 DOI: 10.1039/D0TC05396A

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