THE STRUCTURAL ROLE OF SODIUM DITHIONATE IMPURITY IN THE HABIT MODIFICATION OF SODIUM CHLORATE SINGLE CRYSTALS By Zhipeng Lan Submitted in accordance with the requirements of the degree of Doctor of Philosophy The University of Leeds School of Process, Environmental and Materials Engineering September 2013 The candidate confirms that the work submitted is his/her own, except where work which has formed part of jointly authored publications has been included. The contribution of the candidate and the other authors to this work has been explicitly indicated below. The candidate confirms that appropriate credit has been given within the thesis where reference has been made to the work of others. The calculations for structure factor of the (343)( 341) and (343)(341) secondary planes were completed by Dr. Alan S. de Menezes, and will result in a jointly-authored publication listed (Lan et al., 2014), where the article will be written based on the experimental work by the author. The calculations for PDOS and 2- molecular orbitals of S2O6 were completed by Dr. Che Seabourne using CASTEP codes, and will result in a jointly-authored publication listed (Lan et al., 2014), where the article will be written based on the experimental work by the author. The work herein is the authors own analysis of the data, except where explicitly highlighted in the text. This is summarised below. (i) Chapter 7.5. The structure factor of the ( )( ) and (343)(341) secondary planes included in this section were calculated by Dr. Alan S. de Menezes. 2- (ii) Chapter 8.3.3. The PDOS and molecular orbitals of S2O6 included in this section were calculated by Dr. Che Seabourne. Lan, Z., Lai, X., Roberts, K. J., de Menezes, A. S., dos Santos, A. O., Calligaris, G. A., & Cardoso, L. P. (2014). Determination of the Lattice Distortion in Dithionate-doped Sodium Chlorate Crystals using XRMD. Crystal Growth and Design, Manuscript in preparation. Lan, Z., Lai, X., Seabourne, C. R., Scott, A. J., & Roberts, K. J. (2014). Determination of the Local Structure of the Orientational Dithionate Impurity in the Sodium Chlorate Crystals using Polarized XAFS. Crystal Growth & Design, Manuscript in preparation. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. © 2014 The University of Leeds and Zhipeng Lan ACKNOWLEDGEMENTS Acknowledgements are due to Dr. Xiaojun Lai and Professor Kevin Roberts for their great supervision of this research and teaching of the fundamentals involved in this work. Professor Helmut Klapper, Professor Lisandro Cardoso and Dr. Alan S. de Menezes are acknowledged for their help in interpreting the results from X-ray topography and X-ray multiple-wave diffraction techniques, respectively. Dr. A. O. dos Santos, Guilherme Calligaris and Ian Rosbottom are acknowledged for their help in collecting the data at synchrotrons of LNLS and Diamond, respectively. Acknowledgments are due to Dr. Che Seabourne for providing training on the CASTEP analysis methods. Professor Fred Mosselmans is acknowledged for his kind mentoring on the technical details of XAFS during and after the data collection. Acknowledgements are due to Dr. Vasuki Ramachandran and Neepa Paul for their training on the molecular modelling techniques. Dr. Robert Hammond, Dr. Tim Comyn and Dr. Caiyun Ma are acknowledged for their kind support during this project. Simon Lloyd is acknowledged for his consistent assistance in organizing the local laboratories. The synchrotron facilities of Brazilian Synchrotron Light Laboratory and Diamond Light Source are acknowledged for providing the beamtime for the XRMD and XAFS experiments. Last, but also significantly, acknowledgements are due to my parents and my wife for their supporting me all the way. ABSTRACT A detailed study into the crystal habit modification of the NaClO3 / Na2S2O6 (host / impurity) system is presented. Ordinary morphology of NaClO3 present faces of {001}, {110} and {111} types. The presence of impurity Na2S2O6 has led to rapid development of new faces of {111} type on the NaClO3 crystals grown from solution. Above 70ppm doping concentration, the morphology of NaClO3 crystal is dominated by faces. Crystal twinning occurred under 800ppm doping concentration and above. X-ray topography was used to investigate the growth history and defect configuration of the pure and doped crystals. Lattice distortions at various lattice planes within the pure and doped crystals were determined using X-ray 2- multiple-wave diffraction (XRMD). The local structure of S2O6 in NaClO3 crystal was determined using X-ray absorption fine structure (XAFS). Molecular modelling was applied to investigate the molecular similarity between the impurity and the host. Strong impurity incorporation in the {111} sectors was revealed by X-ray topography. The growth history of doped crystal was reconstructed and interpreted 2- with respect to the inhibiting effect of S2O6 . Disturbance in lattice planes of doped 2- crystals was investigated, which was attributed to the incorporation of S2O6 on { 111} faces. It also revealed different types of local strain on the { } faces along two different directions. The three-dimensional orientation and the actual structure of 2- S2O6 impurity on the {111} faces of NaClO3 crystal were obtained. A structural model for the impurity incorporation was established, showing good consistency with the experimental results. In addition, the segregation coefficient of the impurity was determined by elemental mapping, indicating strong impurity incorporation on the 2- faces rather than others. The incorporated S2O6 was concluded to be capable of disrupting the proper packing structure of the faces, obstructing the generation and propagation of growth steps, and decreasing of driving force for crystal growth. Table of Contents List of Figures………………………………………………………………….I List of Tables………………........………………………………………….VIII Abbreviations and Notation…………………………..………….……………X 1 Introduction ...........................................................................................................1 1.1 Introduction ...................................................................................................2 1.2 Research Background ....................................................................................2 1.3 Aims and Objectives of This Thesis ..............................................................4 1.4 Layout of This Thesis ....................................................................................5 2 Crystal Science and Characterization of Crystallization and Crystal Growth . .................................................................................................................................8 2.1 Introduction ...................................................................................................9 2.2 Fundamental of Crystalline State ..................................................................9 2.2.1 Crystalline Solid .....................................................................................9 2.2.2 Unit Cell .................................................................................................9 2.2.3 Miller Indices........................................................................................10 2.2.4 Crystal Symmetry .................................................................................11 2.2.5 Crystal Systems ....................................................................................12 2.2.6 Isomorphism and Polymorphism ..........................................................14 2.2.7 Crystal Habit .........................................................................................14 2.2.8 Crystal Chemistry .................................................................................18 2.2.9 Crystal Defect .......................................................................................19 2.3 Solubility and Supersaturation ....................................................................20 2.3.1 Solubility ..............................................................................................20 2.3.2 Supersaturation and the Meta-stable Zone ...........................................21 2.3.3 Effect of Impurities on Solubility .........................................................23 2.4 Nucleation ....................................................................................................25 2.4.1 Introduction to Nucleation ....................................................................25 2.4.2 Primary Nucleation ...............................................................................26 2.4.3 Secondary Nucleation ...........................................................................30 2.5 Crystal Growth ............................................................................................31 2.5.1 Introduction to Crystal Growth ............................................................31 2.5.2 Crystal Growth Theories ......................................................................32 2.6 Characterization of Impurity Doped Single Crystal ....................................38 2.6.1 Characterization of Defect Structure by X-Ray Topography ...............38 2.6.2 Synchrotron X-Ray Radiation ..............................................................44 2.6.3 Micro-crystallography by X-Ray Multiple-wave Diffraction ..............45 2.6.4 Determination of the Local