<p>This thesis is concerned with <i>in-situ</i> time-, temperature- and pressure-resolved synchrotron X-ray powder diffraction investigations of a variety of inorganic compounds with twodimensional layer structures and three-dimensional framework structures. In particular, phase stability, reaction kinetics, thermal expansion and compressibility at non-ambient conditions has been studied for 1) Phosphates with composition <i>M</i><i>IV</i>(HPO<sub>4</sub>)<sub>2</sub>·<i>n</i>H<sub>2</sub>O (<i>M</i><i>IV</i> = Ti, Zr); 2) Pyrophosphates and pyrovanadates with composition<i> M</i><i>IV</i>X<sub>2</sub>O<sub>7 </sub>(<i>M</i><i>IV</i> = Ti, Zr and X = P, V); 3) Molybdates with composition ZrMo<sub>2</sub>O<sub>8</sub>. The results are compiled in seven published papers and two manuscripts.</p><p>Reaction kinetics for the hydrothermal synthesis of α-Ti(HPO<sub>4</sub>)<sub>2</sub>·H<sub>2</sub>O and intercalation of alkane diamines in α-Zr(HPO<sub>4</sub>)<sub>2</sub>·H<sub>2</sub>O was studied using time-resolved experiments. In the high-temperature transformation of γ-Ti(PO<sub>4</sub>)(H<sub>2</sub>PO<sub>4</sub>)·2H<sub>2</sub>O to TiP<sub>2</sub>O<sub>7</sub> three intermediate phases, γ'-Ti(PO<sub>4</sub>)(H<sub>2</sub>PO<sub>4</sub>)·(2-x)H<sub>2</sub>O, β-Ti(PO<sub>4</sub>)(H<sub>2</sub>PO<sub>4</sub>) and Ti(PO<sub>4</sub>)(H<sub>2</sub>P<sub>2</sub>O<sub>7</sub>)<sub>0.5</sub> were found to crystallise at 323, 373 and 748 K, respectively. A new tetragonal three-dimensional phosphate phase called τ-Zr(HPO<sub>4</sub>)<sub>2</sub> was prepared, and subsequently its structure was determined and refined using the Rietveld method. In the high-temperature transformation from τ-Zr(HPO<sub>4</sub>)<sub>2</sub> to cubic α-ZrP<sub>2</sub>O<sub>7 </sub>two new orthorhombic intermediate phases were found. The first intermediate phase, ρ-Zr(HPO<sub>4</sub>)<sub>2</sub>, forms at 598 K, and the second phase, β-ZrP<sub>2</sub>O<sub>7</sub>, at 688 K. Their respective structures were solved using direct methods and refined using the Rietveld method. <i>In-situ</i> high-pressure studies of τ-Zr(HPO<sub>4</sub>)<sub>2 </sub>revealed two new phases, tetragonal ν-Zr(HPO<sub>4</sub>)<sub>2 </sub>and orthorhombic ω-Zr(HPO<sub>4</sub>)<sub>2</sub> that crystallise at 1.1 and 8.2 GPa. The structure of ν-Zr(HPO<sub>4</sub>)<sub>2</sub> was solved and refined using the Rietveld method.</p><p>The high-pressure properties of the pyrophosphates ZrP<sub>2</sub>O<sub>7</sub> and TiP<sub>2</sub>O<sub>7</sub>, and the pyrovanadate ZrV<sub>2</sub>O<sub>7 </sub>were studied up to 40 GPa. Both pyrophosphates display smooth compression up to the highest pressures, while ZrV<sub>2</sub>O<sub>7</sub> has a phase transformation at 1.38 GPa from cubic to pseudo-tetragonal β-ZrV<sub>2</sub>O<sub>7</sub> and becomes X-ray amorphous at pressures above 4 GPa.</p><p>In-situ high-pressure studies of trigonal α-ZrMo<sub>2</sub>O<sub>8</sub> revealed the existence of two new phases, monoclinic δ-ZrMo<sub>2</sub>O<sub>8 </sub>and triclinic ε-ZrMo<sub>2</sub>O<sub>8</sub> that crystallises at 1.1 and 2.5 GPa, respectively. The structure of δ-ZrMo<sub>2</sub>O<sub>8 </sub>was solved by direct methods and refined using the Rietveld method.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:su-23 |
| Date | January 2004 |
| Creators | Krogh Andersen, Anne |
| Publisher | Stockholm University, Department of Physical, Inorganic and Structural Chemistry, Stockholm : Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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