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Studies of Inorganic Layer and Framework Structures Using Time-, Temperature- and Pressure-Resolved Powder Diffraction Techniques
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
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.
Keyword [en]
inorganic structure, framework structure, x-ray diffraction, synchrotron radiation, powder diffraction
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:su:diva-23ISBN: 91-7265-795-2 (print)OAI: oai:DiVA.org:su-23DiVA: diva2:191236
Public defence
2004-02-06, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-01-21 Created: 2004-01-21Bibliographically approved
List of papers
1. In-Situ Time-Resolved Synchrotron X-ray Powder Diffraction Studies of Hydrothermal Synthesis of Layered Titanium Phosphates.
Open this publication in new window or tab >>In-Situ Time-Resolved Synchrotron X-ray Powder Diffraction Studies of Hydrothermal Synthesis of Layered Titanium Phosphates.
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-23288 (URN)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-13Bibliographically approved
2. Structural Aspects of the Dehydration and Dehydroxylation of Layered γ-Titanium Phosphate, γ-Ti(PO4)(H2PO4)⋅2H2O.
Open this publication in new window or tab >>Structural Aspects of the Dehydration and Dehydroxylation of Layered γ-Titanium Phosphate, γ-Ti(PO4)(H2PO4)⋅2H2O.
1998 (English)In: Inorganic chemistry, ISSN 1520-510X, Vol. 37, no 17, 4313-4320 p.Article in journal (Refereed) Published
Abstract [en]

The thermal transformations of γ-titanium phosphate, γ-Ti(PO4)(H2PO4)·2H2O, have been studied using thermogravimetric analysis, differential scanning calorimetry, X-ray powder diffraction, and temperature-resolved in-situ powder diffraction. The transformation sequence goes from γ-Ti(PO4)(H2PO4)·2H2O over a new partially dehydrated form γ‘-Ti(PO4)(H2PO4)·(2−x)H2O (x 1) to the anhydrous form β-Ti(PO4)(H2PO4) and then through a two-step condensation process where layered titanium pyrophosphate, Ti(PO4)(H2P2O7)0.5, is formed first and finally cubic titanium pyrophosphate TiP2O7. The dehydration of γ-Ti(PO4)(H2PO4)·2H2O and the dehydroxylation/condensation process from β-Ti(PO4)(H2PO4) to layered titanium pyrophosphate,Ti(PO4)(H2P2O7)0.5, was followed in-situ. A new partially dehydrated phase, γ‘-Ti(PO4)(H2PO4)·(2−x)H2O (x 1), which forms at approximately 50 °C has been detected and characterized. The unit cell is monoclinic with the lattice parameters a = 23.670(1) Å, b = 6.264(1) Å, c = 5.036(1) Å, β = 102.41(1)°, and Z = 4. Layered titanium pyrophosphate, Ti(PO4)(H2P2O7)0.5, which forms at 375 °C has been characterized. The unit cell is monoclinic with lattice parameters a = 16.271(3) Å, b = 6.319(1) Å, c = 5.122(1) Å, β = 90.59(2)°, and Z = 4.

Place, publisher, year, edition, pages
American Chemical Society, 1998
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-23289 (URN)10.1021/ic9801894 (DOI)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved
3. Determination of the Formation Regions of Titanium Phosphates. Determination of the Crystal Structure of β-Titanium Phosphate, Ti(PO4)(H2PO4), from Neutron Powder Data.
Open this publication in new window or tab >>Determination of the Formation Regions of Titanium Phosphates. Determination of the Crystal Structure of β-Titanium Phosphate, Ti(PO4)(H2PO4), from Neutron Powder Data.
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
National Category
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-23290 (URN)10.1006/jssc.1998.7885 (DOI)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved
4. Preparation and Characterization of a New 3-Dimensional Zirconium Hydrogen Phosphate, τ-Zr(HPO4)2; Determination of the Complete Crystal Structure Combining Synchrotron X-ray Single Crystal Diffraction and Neutron Powder Diffraction.
Open this publication in new window or tab >>Preparation and Characterization of a New 3-Dimensional Zirconium Hydrogen Phosphate, τ-Zr(HPO4)2; Determination of the Complete Crystal Structure Combining Synchrotron X-ray Single Crystal Diffraction and Neutron Powder Diffraction.
1998 (English)In: Inorganic chemistry, ISSN 1520-510X, Vol. 37, no 5, 876-881 p.Article in journal (Refereed) Published
Abstract [en]

A new 3-dimensional zirconium hydrogen phosphate, τ-Zr(HPO4)2, was prepared by hydrothermal syntheses. The preparation, characterization, and determination of the crystal structure of this new material are reported. The structure was solved from single-crystal synchrotron diffraction on a 25 × 25 × 50 μm crystal. The position of the hydrogen atom was found using high-resolution neutron powder diffraction data. The unit cell is tetragonal, space group I41cd (No. 110), with lattice parameters a = 11.259(1) Å, c = 10.764(1) Å, and Z = 8. The structure can be described as a 3-dimensional framework built from ZrO6 octahedra bound together by hydrogen phosphate groups (PO3(OH)). The OH groups form a hydrogen-bonded spiral along the 41 axes, with each hydrogen phosphate both donating and accepting hydrogen bonds. The thermal transformations of τ-Zr(HPO4)2 were studied using in-situ temperature-resolved powder diffraction experiments. Hereby the existence of two new phases was discovered. The new phases have been indexed and the unit cell parameters are as follows. Intermediate I:  a = 8.172(1), b = 7.691(1), and c = 10.794(2) Å. Intermediate II: a = 8.283(2), b = 6.620(2), and c = 10.643(2) Å.

Place, publisher, year, edition, pages
American Chemical Society, 1998
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-23291 (URN)10.1021/ic971060h (DOI)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved
5. Ab Initio Structure Determination and Rietveld Refinement of a High-Temperature Phase of Zirconium Hydrogen Phosphate and a New Polymorph of Zirconium Pyrophosphate from In-Situ Temperature-Resolved Powder Diffraction Data.
Open this publication in new window or tab >>Ab Initio Structure Determination and Rietveld Refinement of a High-Temperature Phase of Zirconium Hydrogen Phosphate and a New Polymorph of Zirconium Pyrophosphate from In-Situ Temperature-Resolved Powder Diffraction Data.
2000 (English)In: Acta Crystallographica Section B, ISSN 0108-7681, Vol. 56, no 4, 618-625 p.Article in journal (Refereed) Published
Abstract [en]

The collected in situ temperature-resolved synchrotron powder data revealed that the transformation of the recently reported three-dimensional τ-Zr(HPO4)2 to cubic ZrP2O7 goes through two intermediate phases. The first intermediate phase, ρ-Zr(HPO4)2, is formed in a reversible phase transition at 598  K, which involves both rearrangement and disordering of the hydrogen phosphate groups of τ-Zr(HPO4)2. At 688  K condensation of the hydrogen phosphate groups leads to the formation of the second intermediate, a new polymorph of zirconium pyrophosphate (β-ZrP2O7). Heating above 973  K results in the gradual transformation of β-ZrP2O7 to cubic zirconium pyrophosphate (α-ZrP2O7). The crystal structures of the two intermediate phases were solved from the in situ powder diffraction data using direct methods and refined using the Rietveld method. Both phases are orthorhombic, space group Pnnm and Z = 2. The lattice parameters for the two phases are: ρ-Zr(HPO4)2: a = 8.1935  (2), b = 7.7090  (2), c = 5.4080  (1)  Å; β-ZrP2O7: a = 8.3127  (5), b = 6.6389  (4), c = 5.3407  (3)  Å. The formation mechanism for the new zirconium pyrophosphate polymorph, β-ZrP2O7, is discussed in relation to structurally restricted soft chemistry

Place, publisher, year, edition, pages
Wiley, 2000
Keyword
Rietveld refinement • High-temperature phase • Polymorphism • Powder diffraction • Zirconium hydrogen phosphate • Zirconium pyrophosphate.
National Category
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-23292 (URN)10.1107/S0108768100003645 (DOI)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved
6. The high-pressure structures and properties of τ-Zr(HPO4)2
Open this publication in new window or tab >>The high-pressure structures and properties of τ-Zr(HPO4)2
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-23293 (URN)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-13Bibliographically approved
7. High-pressure properties of TiP2O7, ZrP2O7 and ZrV2O7
Open this publication in new window or tab >>High-pressure properties of TiP2O7, ZrP2O7 and ZrV2O7
2001 (English)In: Journal of Applied Crystallography, ISSN 0021-8898, Vol. 34, no 1, 7-12 p.Article in journal (Refereed) Published
Abstract [en]

High-pressure synchrotron X-ray powder diffraction studies of TiP2O7, ZrP2O7 and ZrV2O7 have been performed. The ZrV2O7 structure undergoes a reversible transition at 1.38–1.58  GPa from cubic α- to pseudo-tetragonal β-ZrV2O7 that displays an orthorhombic 2 × 3 × 3 supercell. At pressures above 4  GPa, ZrV2O7 becomes irreversibly X-ray amorphous. No such transformations are observed for TiP2O7 and ZrP2O7, which compress smoothly up to the highest investigated pressures (40.3 and 20.5  GPa, respectively). These differences in high-pressure properties are discussed in terms of the negative thermal expansion of ZrV2O7. The bulk moduli at ambient pressure (B0) for TiP2O7, ZrP2O7, α-ZrV2O7 and β-ZrV2O7 were estimated to be 42  (3), 39  (1), 17.0  (7) and 20.8  (10)  GPa, respectively.

Place, publisher, year, edition, pages
Wiley, 2001
Keyword
phase transformations • high-pressure diffraction • titanium pyrophosphate • zirconium pyrophosphate • zirconium pyrovanadate • negative thermal expansion • pressure amorphization.
Identifiers
urn:nbn:se:su:diva-23294 (URN)10.1107/S0021889800013856 (DOI)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved
8. High-Pressure Transitions of Trigonal α-ZrMo2O8
Open this publication in new window or tab >>High-Pressure Transitions of Trigonal α-ZrMo2O8
2000 (English)In: Physical review B Condensed matter and materials physics, ISSN 1098-0121, Vol. 61, no 17, 11209-11212. p.Article in journal (Refereed) Published
Abstract [en]

High-pressure synchrotron x-ray powder-diffraction studies show that trigonal α-ZrMo2O8 transforms to a monoclinic symmetry phase (δ-ZrMo2O8) at 1.06–1.11 GPa. The space group was determined to C2/m. A further high-pressure transition from the monoclinic δ to a triclinic ε phase occur at 2.0–2.5 GPa (space group P1 or P1¯). Both transformations are reversible. The volume compressibilities are similar for the α and δ phase, and five times lower for the ε phase.

Place, publisher, year, edition, pages
American Physicl Society, 2000
Identifiers
urn:nbn:se:su:diva-23295 (URN)10.1103/PhysRevB.61.11209 (DOI)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved
9. High-Pressure Structures of α- and δ-ZrMo2O8
Open this publication in new window or tab >>High-Pressure Structures of α- and δ-ZrMo2O8
2001 (English)In: Acta Crystallographica Section B Structural science, ISSN 0108-7681, Vol. 57, no 1, 20-26 p.Article in journal (Refereed) Published
Abstract [en]

In situ high-pressure synchrotron X-ray powder diffraction studies of trigonal α-ZrMo2O8, zirconium molybdate, have been performed from ambient conditions to 1.9  GPa, over the α–δ phase transition at 1.06–1.11  GPa. The monoclinic structure of δ-ZrMo2O8, stable between 1.1 and 2.5  GPa  at 298  K, has been solved by direct methods and refined using the Rietveld method. Significant distortions of the ZrO6 and MoO4 polyhedral elements are observed for δ-ZrMo2O8, as compared to the ambient conditions of the α-phase, while the packing of anions becomes more symmetric at high pressure.

Place, publisher, year, edition, pages
Wiley, 2001
Keyword
high-pressure diffraction • distortion • framework structures.
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:su:diva-23296 (URN)10.1107/S0108768100013215 (DOI)
Note
Part of urn:nbn:se:su:diva-23Available from: 2004-01-21 Created: 2004-01-21 Last updated: 2010-01-08Bibliographically approved

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