Epitaxy of Rhodochrosite (MnCO₃) on Muscovite Mica and Its Relation with Calcite (CaCO₃)

Abstract

The flatness of muscovite mica makes it a convenient substrate to study epitaxy. We have analyzed the growth of rhodochrosite (MnCO 3 ) crystals in solution and on muscovite mica. Growth at high supersaturations occurs via the formation of amorphous MnCO 3 , which over time transforms into the crystalline form. In the presence of muscovite mica, epitaxial rhodochrosite crystals with a size of approximately 1 μm form. These crystals are kinetically roughened, because of the high supersaturation. The lattice match between MnCO 3 and muscovite was found not to be the main reason for epitaxy. If the growth experiment is performed twice, the original epitaxial MnCO 3 crystals are overgrown by many small crystallites. Similarly, spherical MnCO 3 crystals with many overgrown facets can be formed on a muscovite surface that is exposed to humidity or by using a higher MnCO 3 supersaturation. A comparison with calcite shows that epitaxy strongly depends on initial supersaturation for both carbonates. In contrast to previous studies, we find that at the right supersaturation, epitaxial calcite crystal growth is possible on freshly cleaved muscovite.

Electrochemically Assisted Growth of Hopper and Tabular Calcite under Confinement

“…Both (001) mica and (111) gold surfaces have been shown to promote the oriented growth of (001)-oriented rhombohedral calcite. Epitaxy of calcite has been detected on weathered mica, with K 2 CO 3 nanocrystallites facilitating oriented calcite growth, or on freshly cleaved mica at higher supersaturations. , Negatively polarized Au(111) films deposited onto mica have been shown to promote oriented growth of calcite with (001) planes parallel to the substrate, while polycrystalline gold or Au(111) evaporated onto silicon substrates yielded vaterite and calcite with random orientations. , In our electrochemical SFA setup, both freshly cleaved mica and mica-template-stripped (111) polarized Au films support the formation of oriented calcite crystals with (001) planes parallel to these two substrates. Both the pseudohexagonal lattice of muscovite mica (001) and the hexagonal lattice of Au(111) could provide a good epitaxial match for calcite (001), which also displays a hexagonal symmetry.…”

“…Epitaxy of calcite has been detected on weathered mica, with K 2 CO 3 nanocrystallites facilitating oriented calcite growth, 69 or on freshly cleaved mica at higher supersaturations. 70,71 Negatively polarized Au(111) films deposited onto mica have been shown to promote oriented growth of calcite with (001) planes parallel to the substrate, 68 while polycrystalline gold or Au(111) evaporated onto silicon substrates yielded vaterite and calcite with random orientations. 29,68 In our electrochemical SFA setup, both freshly cleaved mica and micatemplate-stripped (111) polarized Au films support the formation of oriented calcite crystals with (001) planes parallel to these two substrates.…”