The Effect of Zr-Doping and Crystallite Size on the Mechanical ...

Content
Content
Zusammenfassung ............................................................................................................ 4
Summary........................................................................................................................... 8
I. Introduction ................................................................................................................. 12
1. TiO2 <strong>and</strong> <strong>Zr</strong>O2 Polymorphs .................................................................................... 12
1.1. Polymorphs <strong>of</strong> Titania ..................................................................................... 12
1.2. Polymorphs <strong>of</strong> Zirconia................................................................................... 15
1.3. Energetics <strong>of</strong> Nanocrystalline <strong>Zr</strong>O2 <strong>and</strong> TiO2 Phases ..................................... 16
2. TiO2-<strong>Zr</strong>O2 Phase Diagram...................................................................................... 19
3. Technical Applications........................................................................................... 21
4. Tuning <strong>of</strong> Elastic Properties ................................................................................... 23
5. Computational Work .............................................................................................. 27
6. Motivation <strong>and</strong> Outline........................................................................................... 29
II. Methods <strong>and</strong> Instrumentation .................................................................................... 30
1. High Pressure Experimental Techniques................................................................ 30
1.1. Hydrothermal Experiments ............................................................................. 31
1.2. Piston Cylinder Technique .............................................................................. 32
1.3. Multi Anvil Technique .................................................................................... 34
1.4. Diamond Anvil Cell ........................................................................................ 36
2. Analytical Methods ................................................................................................ 38
2.1. Powder X-Ray Diffraction .............................................................................. 38
2.2. X-Ray Absorption Spectroscopy..................................................................... 40
2.3. Raman Spectroscopy ....................................................................................... 41
2.4. Electron Microprobe........................................................................................ 41
2.5. Transmission Electron Microscopy................................................................. 42
3. Ab-initio Calculations ............................................................................................ 43
4. Compressing Materials: Equation <strong>of</strong> State ............................................................. 44
III. Results <strong>and</strong> Discussion ............................................................................................. 46
1. Synthesis <strong>and</strong> Characterization <strong>of</strong> Starting Materials............................................. 46
1.1. Sol-Gel Synthesis <strong>of</strong> TiO2-<strong>Zr</strong>O2 Powders ....................................................... 46
1.2. Synthesis <strong>of</strong> Microscale Anatase <strong>and</strong> Nanoscale Rutile Ti0.9<strong>Zr</strong>0.1O2 .............. 55
2. Experimental Results on the System TiO2-<strong>Zr</strong>O2 to 10 GPa ................................... 57
3. Compression Behavior <strong>of</strong> Anatase <strong>and</strong> Rutile........................................................ 60
3.1. Compression Behavior <strong>of</strong> <strong>Zr</strong>-doped Anatase .................................................. 61
3.2. Compression Behavior <strong>of</strong> TiO2 Nanoscale Rutile........................................... 75
3.3. Compression behavior <strong>of</strong> <strong>Zr</strong>-doped microscale rutile ..................................... 77
4. Pressure Induced Transformations <strong>of</strong> Anatase <strong>and</strong> Rutile...................................... 80
4.1. Multi Anvil Experiments on Phase Transition <strong>of</strong> Anatase <strong>and</strong> Rutile to TiO2II
................................................................................................................................ 80
4.2. DAC Experiments on Phase Transitions <strong>of</strong> <strong>Zr</strong>-doped Anatase ....................... 84
4.3. DAC Experiments on Phase Transitions <strong>of</strong> Rutile .......................................... 86
5. Computational Ground States <strong>of</strong> TiO2 ................................................................... 90
IV. Conclusions .............................................................................................................. 96
Acknowledgments ........................................................................................................ 101
Bibliography ................................................................................................................. 102
Erklärung ...................................................................................................................... 115
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