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Characterization of the structural environment of dithionate ions associated with their role in the crystal habit modification of sodium chlorate

DOI: 10.1021/acs.cgd.7b01770 DOI Help

Authors: Zhipeng Lan (University of Leeds) , Guilherme A. Calligaris (University of Campinas – UNICAMP) , Alan S. De Menezes (University of Campinas – UNICAMP) , Adenilson O. Dos Santos (CCSST, Federal University of Maranhão – UFMA) , Xiaojun Lai (University of Leeds) , Lisandro P. Cardoso (University of Campinas – UNICAMP) , Kevin J. Roberts (University of Leeds)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Crystal Growth & Design

State: Published (Approved)
Published: May 2018

Abstract: Sodium chlorate (NaClO3) crystals change from a cuboid to a tetrahedron of {1 ̅1 ̅1 ̅} morphology when crystallized in the presence of sodium dithionate (Na2S2O6) impurity. Polarized Extended X-Ray Absorption Fine Structure at the S K-edge, used to probe the local structure around this impurity with respect to its orientation within the bulk crystal lattice, reveals that the S-S bond of the S2O62- ions is closely aligned along the <111>/<1 ̅1 ̅1 ̅> lattice direction. High resolution diffraction studies using X-ray Multiple Diffraction reveal growth-induced anisotropy in the doped crystals associated with subtle lattice distortions in the symmetry-independent {1 ̅1 ̅1 ̅} and {111} growth sectors. The data is consistent with a mechanistic model involving creation of lattice vacancies and the substitution of one of the SO3 anionic groups of the dopant ion for a host ClO3 ion when incorporated at the {1 ̅1 ̅1 ̅} growth interface with the other SO3 group substituting for one or more anionic sites in the succeeding growth layer depending on the degree of impurity concentration within the crystallization solution. This mechanism is also fully consistent with the formation of twinning at higher impurity concentrations previously reported by Lan et.al.

Journal Keywords: Crystal Growth; Habit Modification; EXAFS; X-ray Multiple Diffraction; Sodium Chlorate

Subject Areas: Chemistry


Instruments: I18-Microfocus Spectroscopy

Other Facilities: LNLS