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| Abstract |
Surface structure of phlogopite was imaged using an atomic force microscope (AFM) in contact mode in water. The AFM image data were compared with the bulk structure data of phlogopite obtained by the ...Rietveld refinement of X-ray powder diffraction (XRD). The following two types of AFM images were observed: Image (1) in which a hexagonal array of bright spots corresponds to the hexagonal rings of SiO4 tetrahedra; Image (2) in which bright spots hexagonal arranged on about 5.3A centers. The mean unit cell dimensions (a=5.32(8)A, b=9.23 (12)A) for the phlogopite surface measured from the image (1) are nearly equal to those (a=5.332 (2)A b=9.236(3)A) for the bulk structure determined by XRD. However, the unit cell dimensions for the phlogopite surface slightly vary, showing gradual shortening and elongation of cell dimensions. Slight variations of the distances and bond angles between adjacent SiO4 tetrahedra are also found on the phlogopite surface. These variations are caused by that the surface relaxed by rotation of SiO4 tetrahedra in the a-b plane after cleaving and/or by the AFM measurement error. Slight tilting of SiO4 tetrahedra out of the a-b plane may also occur after cleaving and may affect the surface readjustment. However, the degree of surface relaxation in trioctahedral mica phlogopite was much smaller than that in dioctahedral mica muscovite investigated in our previous work. Image (2) was made by varying the scan angles, even on the same surface in which the image (1) was obtained. Therefore, what is depicted in the image (2) is not the arrangement of interlayer K ions but the basal plane of the tetrahedral sheet. A hexagonal array of bright spots separated by 3 distance of about 5.3 A can correspond to a hexagonal array of individual blocks composed of three basal oxygen ions.show more
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