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Crystallographic Studies of Selected Perovskite-Group Compounds / by Shannon Farrell

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Crystallographic Studies of Selected Perovskite-Group Compounds / by Shannon Farrell Lakehead University Knowledge Commons,http://knowledgecommons.lakeheadu.ca Electronic Theses and Dissertations Retrospective theses 1997 Crystallographic studies of selected perovskite-group compounds / by Shannon Farrell. Farrell, Shannon Patrick http://knowledgecommons.lakeheadu.ca/handle/2453/2539 Downloaded from Lakehead University, KnowledgeCommons INFORMATION TO USERS This manuscript has been reproduced from the microfihn master. UMI fîhns the text directly from the orignal or copy submitted. Thus, some thesis and dissertation copies are in typewriter &ce, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, b%inning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Infonnation C o m paiy 300 North Zeeb Road, Ann Arbor MI 48106-1346 USA 313/761-4700 800/521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS The original manuscript received by UMI contains pages with indistinct print Pages were microfilmed as received. This reproduction is the best copy available UMI L Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. k Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CRYSTALLOGRAPHIC STUDIES OF SELECTED . f PEROVSKITE-GROUP COMPOUNDS . by Shannon Farrell © A thesis submitted In partial fulfilment of the requirements for the degree of Master of Science Supervisor. Dr. R.H. Mitchell Lakehead University Thunder Bay, Ontario Canada November 1997 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. National Library Bibliothèque nationale 1 * 1 of Canada du Canada Acquisitions and Acquisitions et Bibliographic Services services bibliographiques 395 Wellington Street 395, rue Wellington Ottawa ON K1A0N4 Ottawa ON K1A0N4 Canada Canada Yourfiie Votn réfénnc» OurOe Notre référence The author has granted a non­ L’auteur a accordé une hcence non exclusive hcence allowing the exclusive permettant à la National Library of Canada to Bibhothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies o f this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfîche/fîlm, de reproduction sur papier ou sur format électronique. The author retains ownership o f the L’auteur conserve la propriété du copyright in this thesis. Neidier the droit d’auteur qui protège cette thèse. thesis nor substantial extracts from it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author’s ou autrement reproduits sans son permission. autorisation. 0-612-33371-X CanadS Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CRYSTALLOGRAPHIC STUDIES OF SELECTED PEROVSKITE-GROUP COMPOUNDS Abstract This study investigates the tausonite-lopante solid solution series. Members of this series are important in some alkaline complexes, thus making studies of their crystallography essential. Rietveid refinement of the crystal structures of the tausonite- loparite solid solution senes, using X-ray diffraction powder patterns, indicates that there is a reduction in symmetry from cubic {Pm3m) to orthorhombic {Pnma), by way of an intermediate tetragonal (P4/mbm) modification. The symmetry changes appear to occur at about - 6 6 . 6 and "-33.3 wt% tausonite, which are consistent with formulae of approximately SrjCNaLalTiaOg and SrCNaLaljTigOg, respectively. The pseudo-cubic cell parameter 8 p decreases with increasing loparite content, while the [111] tilt angle in Pm3m) on inception at 50 wt% loparite achieves a maximum and decreases thereafter with increasing loparite content Rietveid refinements indicate that no ordering at the A-site exists throughout the solid solution series. This study also investigates a titanium perovskite (NagqThiQTiOa), which is unusual in that it contains a tetravalent cation at the A-site. This thorium titanium perovskite was synthesised in an attempt to determine its structure. Although powder diffractometry suggests an Fm3m space-group, attempts at Rietveid refinement of the structure show the actual space-group must be of reduced symmetry. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This study also provides data on the pseudo-binary system between hollandite (KgCrgTigOig) and the n=3 member of the homologous series KgLagTia+nOiofZn, KgLg^TyOig. This series is important in understanding the location and environment of the rare-earth cations in natural hollandite specimens and the capability of hollandite (i.e., SynRoc) to immobilize large elements of varying charge and size. This pseudo-binary system is characterized by the presence of the following phases: hollandite [Ki a4(Cr1 /«Tig^2 )7.9 5 ^ 16]^ perovskite- 1 [(Kozsi-3 oj5 )o3 i(Croj)5TiQjg)i^0 3 ]; potassium hexatitanate (K^^gT^Oig); perovskite-2 (LaCrOj); and perovskite-3 (L%T^Oy). Complete solid-solution between the end-members of this system does not occur. The holiandites (space-group 14/m) have an A-site occupancy of approximately 75-82%, and exhibit no significant substitution of La^ at any of the cation sites. Perovskite-1 is considered to be a non-stoichiometric A-site deficient perovskite. Potassium hexatitanate is the only main phase that is stoichiometric and contains no substitution of Cr^ in any of the cation sites. All the Cr^ excluded from the potassium hexatitanate structure is incorporated into perovskite-2 . n Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Acknowledgements I am grateful to Dr. Roger H. Mitchell who supervised this research project and whose support and guidance throughout the study made this thesis possible. His patience and many valuable suggestions on earlier drafts of this thesis are appreciated. Special thanks to Alan MacKenzie and Keith Pringnitz of the Lakehead University Instrumentation Laboratory for their instruction, advice, and assistance with X-Ray Diffractometry and Scanning Electron Microscopy techniques. I am also indebted to Dr. Anton Chakhmouradian of St Petersburg State University, Russia for his generous help concerning structure refinements, and to Dr. Mati Raudsepp of the University of British Columbia and Neil Ball of the University of Manitoba for their advice regarding Rietveid refinement. To the faculty, staff, and students of the Geology department I extend my appreciation for their freely given counsel when requested. I thank my family for their sustained support and trust in me, especially when far from my home in Nova Scotia. I am especially grateful to my wife Michelle, who providing relief from the tension and anxiety and her continued expression of faith in me. m Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table of Contents Page Abstract ....................................................................................................................... I List of Figures.......................................................................................................... IX List of Tables ............................................................................................................ XII Chapter 1 : Perovskite -An Introduction 1.1. Perovskite -Scientific and Economic Importance..................................... 1 1.2. Perovskite .............................................................................................. 3 1.2.1. Ideal Perovskite-type Structure ................................................ 3 1.2.2. ReOg-type Structure.................................................................. 8 1.2.3. Distorted Perovskite Structures............................................... 11 1.2.4. Naturally-Occurring Perovskites ............................................. 13 1.3. Objectives ............................................................................................ 15 Chapter 2 : Experimental Procedures 2.1. Sample Preparation.............................................................................. 16 2.1.1. Introduction ............................................................................ 16 2.1.2. Synthesis Techniques...........................................................
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