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Figure 3
Oblate microspheroids in the intermediate stages. CXDI images of vaterite microspheroids obtained from the syntheses (a)–(d) 8 mM 1 g l−1 2 h and (e)–(h) 8 mM 1 g l−1 8 h with (a), (b), (e) and (f) 3D views showing the wall thickness of the shell from 0 to 250 nm. (c) and (g) CXDI 2D slices viewed in the xz plane. The inset of (c) shows a TEM image of the edge of a core. This allows access to the size of the nanoparticles of the core (details provided in Fig. S3). (d) and (h) 3D views of the core depicted in blue, with half the shell cut away to allow observation of the inside. The yellow arrows indicate the poles. In (e), the inset shows vaterite crystals extracted from the microspheroid (in green) and the platelet-associated crystal geometry (in white). The vectors a, b and c refer here to the crystallographic axes of vaterite according to Kamhi's model [P63/mmc space group (Kamhi, 1963BB28)]. The inset of (f) displays a scheme of the microspheroid. The arrows represent the dipole moments associated with the vaterite nanoparticles. The poles are free of nanoparticles to reduce the dipole energy. Note S:Ca = 0.59. Scale bar = 2 µm for (a)–(d) and 1 µm for (e)–(h).

IUCrJ
Volume 9| Part 5| September 2022| Pages 580-593
ISSN: 2052-2525
https://doi.org/10.1107/S2052252522006108