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Determination of the Formation Regions of Titanium Phosphates. Determination of the Crystal Structure of β-Titanium Phosphate, Ti(PO4)(H2PO4), from Neutron Powder Data.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
1998 (English)In: Journal of solid state chemistry, ISSN 1095-726X, Vol. 140, no 2, 266-271 p.Article in journal (Refereed) Published
Abstract [en]

The formation region of the various types of layered titanium hydrogen phosphate hydrates was investigated. The materials were prepared by hydrothermal methods, treating amorphous titanium phosphate with phosphoric acid (8 to 16M) in the temperature range 175 to 250°C. The materials obtained were:α-Ti(HPO4)2·H2O,γ-Ti(PO4)(H2PO4)·2H2O, and its anhydrous formβ-Ti(PO4)(H2PO4). The structure ofβ-Ti(PO4)(H2PO4) has been determined by Rietveld powder refinement of high resolution neutron diffraction data. The structure is refined in the monoclinic space groupP21/n(No. 14). The unit cell parameters are:a=18.9503(4) Å,b=6.3127(1) Å,c=5.1391(1) Å,β=105.366(2)°;Z=4. The final agreement factors were:Rp=2.9% andRwp=3.8%. The structure ofβ-Ti(PO4)(H2PO4) is built from TiO6octahedra linked together by tertiary phosphate (PO4) and dihydrogen phosphate ((OH)2PO2) tetrahedra. The layers are held together by hydrogen bonds.

Place, publisher, year, edition, pages
Elsevier , 1998. Vol. 140, no 2, 266-271 p.
National Category
Physical Chemistry
URN: urn:nbn:se:su:diva-23290DOI: 10.1006/jssc.1998.7885OAI: diva2:191229
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved
In thesis
1. Studies of Inorganic Layer and Framework Structures Using Time-, Temperature- and Pressure-Resolved Powder Diffraction Techniques
Open this publication in new window or tab >>Studies of Inorganic Layer and Framework Structures Using Time-, Temperature- and Pressure-Resolved Powder Diffraction Techniques
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is concerned with in-situ 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 MIV(HPO4)2·nH2O (MIV = Ti, Zr); 2) Pyrophosphates and pyrovanadates with composition MIVX2O7 (MIV = Ti, Zr and X = P, V); 3) Molybdates with composition ZrMo2O8. The results are compiled in seven published papers and two manuscripts.

Reaction kinetics for the hydrothermal synthesis of α-Ti(HPO4)2·H2O and intercalation of alkane diamines in α-Zr(HPO4)2·H2O was studied using time-resolved experiments. In the high-temperature transformation of γ-Ti(PO4)(H2PO4)·2H2O to TiP2O7 three intermediate phases, γ'-Ti(PO4)(H2PO4)·(2-x)H2O, β-Ti(PO4)(H2PO4) and Ti(PO4)(H2P2O7)0.5 were found to crystallise at 323, 373 and 748 K, respectively. A new tetragonal three-dimensional phosphate phase called τ-Zr(HPO4)2 was prepared, and subsequently its structure was determined and refined using the Rietveld method. In the high-temperature transformation from τ-Zr(HPO4)2 to cubic α-ZrP2O7 two new orthorhombic intermediate phases were found. The first intermediate phase, ρ-Zr(HPO4)2, forms at 598 K, and the second phase, β-ZrP2O7, at 688 K. Their respective structures were solved using direct methods and refined using the Rietveld method. In-situ high-pressure studies of τ-Zr(HPO4)2 revealed two new phases, tetragonal ν-Zr(HPO4)2 and orthorhombic ω-Zr(HPO4)2 that crystallise at 1.1 and 8.2 GPa. The structure of ν-Zr(HPO4)2 was solved and refined using the Rietveld method.

The high-pressure properties of the pyrophosphates ZrP2O7 and TiP2O7, and the pyrovanadate ZrV2O7 were studied up to 40 GPa. Both pyrophosphates display smooth compression up to the highest pressures, while ZrV2O7 has a phase transformation at 1.38 GPa from cubic to pseudo-tetragonal β-ZrV2O7 and becomes X-ray amorphous at pressures above 4 GPa.

In-situ high-pressure studies of trigonal α-ZrMo2O8 revealed the existence of two new phases, monoclinic δ-ZrMo2O8 and triclinic ε-ZrMo2O8 that crystallises at 1.1 and 2.5 GPa, respectively. The structure of δ-ZrMo2O8 was solved by direct methods and refined using the Rietveld method.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2004. 68 p.
inorganic structure, framework structure, x-ray diffraction, synchrotron radiation, powder diffraction
National Category
Chemical Sciences
urn:nbn:se:su:diva-23 (URN)91-7265-795-2 (ISBN)
Public defence
2004-02-06, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Available from: 2004-01-21 Created: 2004-01-21Bibliographically approved

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