A Comparative Rietveld Refinement Study of Natisite Prepared in Different Morphology.

Two morphological types of the synthetic analogue of the mineral natisite NaTiSiO have been prepared in the system NaO-TiO-SiO-HO. The crystal structures of the obtained pillow ( A)- and coin ( B)-shaped particles have been refined with similar parameters by the method of Rietveld, compared to each other and to the available single crystal X-ray diffraction data. Sample B showed bigger unit cell with longer a = b and shorter c-axis when compared with phase A. The shorter a = b axes in phase A led to compensative elongation of the c-axis and notably longer terminal bond distance in the TiO semi-octahedra. Analysis of the refined structural parameters showed that Ti-O bond of the unshared apical oxygen is the most responsive to the lattice strain. Additionally, the overall mechanism of structural response to the observed microstructural distortions is discussed. Graphical Abstract: The possible influence of different particle morphology on the Rietveld refinement results of synthetic natisite has been evaluated[Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]