“New insights into thorium and uranium oxo-arsenic (III/V) and oxo-phosphates (V) crystal chemistry” Von der Fakultät für Georessourcen und Materialtechnik der Rheinisch-Westfälischen Techenischen Hochschule Aachen zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften Genehmigte Dissertation vorgelegt von Master Na Yu aus Sichuan Berichter: Prof. Dr. rer. nat. Evgeny V. Alekseev Univ. -Prof. Dr. rer. nat. Dirk Bosbach Prof. Dr. Thorsten M. Gesing Univ. -Prof. Dr. rer. nat. Georg Roth Tag der mündlichen Prüfung: 11. Dezember 2015 Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar i © Copyright 2015 Na Yu ii NEW INSIGHTS INTO THORIUM AND URANIUM OXO-ARSENIC (III/ V) AND OXO- PHOSPHATES (V) CRYSTAL CHEMISTRY Abstract The fundamental chemistry of actinides is of great interest owing to the diverse number of valence states and complex coordination chemistry of the actinides. The phases based on actinides and oxo-salt fragments have been under thorough investigation in the last decades. These compounds can be widely found in nature and they affect the migration process of actinides in nature. A better understanding of the fundamental coordination chemistry of actinide compounds with oxo-salts of group V elements is not only important for understanding the actinides behavior within the migration process but can also be used to understand actinide properties in phosphate ceramics. Concerning the radioactive issues, the less radioactive early actinides (i.e. U, Th) can be taken as modeling elements to study the crystal chemistry of the transuranic elements (Np, Pu) without the major handling problems. This can be done as Th(IV) has a very similar coordination chemistry with An(IV) and U(VI) can be chosen as a modeling element for transuranic elements in higher valence states. Therefore, a systematic research on the actinides (U, Th) bearing phases with tetrahedral oxo-anions such as phosphates and arsenates have been performed in this work. High temperature (HT) solid state reaction, High pressure high temperature (HP-HT) solid state reaction and the hydrothermal method were the methods of choice for synthesizing actinide bearing oxo-arsenic(III/V) and oxo- phosphorus(V) phases in the past three years. As a result, numerous novel compounds containing actinides were obtained. The structures of all compounds were determined using single crystal X-ray diffraction data. Raman spectroscopy, EDS, DSC and high temperature powder X-ray diffraction (HT-PXRD) measurements were implemented to characterize the chemical and physical properties of the obtained compounds. The core of this dissertation is a fundamental study of the crystal chemistry of actinides (Th, U) oxo-arsenic (III/V) and oxo-phosphate(V) phases that were derived from the before mentioned methods. They can be separated into several main parts according to the structural features: layers in U(VI) phases (chapter 3); cations driving structural diversity of thorium arsenates and n- phosphates (chapter 4 and 5); uranium metaphosphate with (PO3)n polymeric chains (chapter 6); mixed-valent arsenic(III/V) Th compounds obtained under extreme pressure (chapter 7); series of compounds adopting the typical structure type of KTh2(AsO4)3 and presented by IV ATh2(AsO4)3(A= K, Rb, Cs, Ag), LiTh2(PO4)3 and BU 2(PO4)3 (B= Rb, Cs); tri-phosphate and tri- arsenate T3O10 units in the ATh(T3O10) (A= Rb, Cs; T= P, As) family (chapter 7). i CONTENTS FIGURES ........................................................................................................................................... v TABLES ............................................................................................................................................. x ACKNOWLEDGMENTS ...................................................................................................................... i Chapter 1 INTRODUCTION .............................................................................................................. 1 1.1 Overview ................................................................................................................................ 1 1.2 Background I: Structural Chemistry of Uranium and Thorium ............................................. 2 1.2.1 Oxidation States of Uranium and Thorium .................................................................... 2 1.2.2 Coordination Numbers and Coordination Polyhedra of Uranium and Thorium ........... 3 1.3 Background II: Structural Chemistry of Phosphates/Phosphites and Arsenate/ Arsenites .. 5 1.4 Background III: Overview of some known Uranium and Thorium bearing Phosphates/Phosphites and Arsenates/Arsenites ...................................................................... 7 1.5 References ............................................................................................................................. 8 Chapter 2 SYNTHETIC METHODS AND CHARACTERIZATION TECHNIQUES .................................. 11 2.1 Synthetic Methods .............................................................................................................. 11 2.1.1 Hydrothermal Synthetic Method ................................................................................. 11 2.1.2 High Temperature (HT) Solid State Synthesis .............................................................. 11 2.1.3 High-Temperature High-Pressure (HTHP) Synthetic Method ...................................... 12 2.2 Systematic Synthesis of Thorium and Uranium bearing Phosphates and Arsenates ......... 14 2.3 Characterization Techniques ............................................................................................... 17 2.3.1 Single Crystal X-ray Diffraction ..................................................................................... 18 2.3.2 Powder X-ray Diffraction .............................................................................................. 20 2.3.3 Raman and IR Spectroscopy ......................................................................................... 21 2.3.4 Element analysis ........................................................................................................... 22 2.3.5 TG-DCS Experiment ...................................................................................................... 23 2.4 Structure Determination from Single Crystals .................................................................... 24 2.5 Bond Valence Analysis ......................................................................................................... 25 2.6 References ........................................................................................................................... 26 i Chapter 3 TOPOLOGICALLY IDENTICAL, BUT GEOMETRICALLY ISOMERIC LAYERS IN ANHYDROUS Rb[UO2(AsO3OH)(AsO2(OH)2)] AND HYDROUS α- and β-Rb[UO2(AsO3OH)(AsO2(OH)2)]·H2O ....... 27 3.1 Abstract ............................................................................................................................... 27 3.2 Introduction ......................................................................................................................... 27 3.3 Synthesis .............................................................................................................................. 28 3.4 Single Crystal X-ray Diffraction ............................................................................................ 30 3.5 Chemical Composition ......................................................................................................... 32 3.6 Bond Valence Analysis ......................................................................................................... 33 3.7 Structure Description .......................................................................................................... 37 3.8 Graph Representation of Structure Topology, Geometric Isomerism and Topotactic Dehydration Reactions .............................................................................................................. 43 3.9 Raman Spectroscopy ........................................................................................................... 47 3. 10 Conclusions ....................................................................................................................... 49 3.11 References ......................................................................................................................... 50 Chapter 4 MORPHOTROPY AND TEMPERATURE DRIVEN POLYMORPHISM IN A2Th(AsO4)2 (A= Li, Na, K, Rb, Cs) SERIES ...................................................................................................................... 52 4.1 Abstract ............................................................................................................................... 52 4.2 Introduction ......................................................................................................................... 52 4.3 Synthesis .............................................................................................................................. 53 4.4 Single Crystal X-ray Diffraction ............................................................................................ 54 4.5 Chemical Compositions ....................................................................................................... 55 4.6 Pure Powder Samples Preparation and Powder X-ray Diffraction ....................................