Structural studies of framework materials
Structural studies of framework materials
Phosphate compounds described by the formula RbNixCu1-xPO4 have been synthesised via a gel route for x = 1 to x = 0. The end members of the series were found to be isostructural with the ABW zeolite, LiAlSiO4-H2O, with space group Pc21n. The intermediate members of the serious either have the same ABW structure type, or crystallise in the space group P1211 with an ABW related structure consisting of phosphate tetrahedra and a combination of metal tetrahedra and square based pyramids. Thermal analysis in combination with variable temperature diffraction has shown that all members of the series undergo a phase transition at elevated temperatures. This structural change was investigated in detail for RbNi0.2Cu0.8PO4, which transforms at approximately 480°C to a phase isostructural with Polymorph 1 of CsZnPO4.
The synthetic aluminosilicate CsAlSi5O12, synthesised via a gel route, with the CAS framework type has been found to have a non-random distribution of aluminium across the three tetrahedral sites. A combination of high-resolution neutron diffraction and MASNMR has shown that the aluminium in the structure sits solely on the second of the three sites. The structure of the gallosilicate CsGaSi5O12 has been found to be isostructural with the CAS material. The structure based on X-ray diffraction shows a different distribution of gallium in the structure to that found for aluminium in CsAlSi5O12 with the majority of the gallium on the first and third tetrahedral sites.
A novel metal arsenate LiCoAsO4 has been synthesised and found to crystalline in the Pnma spacegroup. The material has a structure related to the olivine mineral, Mg2SiO4. Two isostructural metal arsenates, MM6’(OH)3(AsO4)(AsO4H) (M=M’=Co, Ni) have also been synthesised. The structures, determined from single crystal diffraction, show that the materials crystallise in the P63mc space group and are related to the mineral dumortierite. Both materials undergo a magnetic transition on cooling to a canted antiferromagnetic state. The new iron arsenate Fe7(HAsO4)4(AsO4)2, has been characterised as a three-dimensional network of arsenate tetrahedra linking iron octahedra and trigonal bipyramids. A piperazine arsenate material has been synthesised by a slow evaporation technique. The structure consists of a network of hydrogen bonded arsenate, water and piperazine groups.
University of Southampton
Hughes, Robert William
257849c4-78a1-49a8-a370-992cfc75ab8e
2003
Hughes, Robert William
257849c4-78a1-49a8-a370-992cfc75ab8e
Hughes, Robert William
(2003)
Structural studies of framework materials.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Phosphate compounds described by the formula RbNixCu1-xPO4 have been synthesised via a gel route for x = 1 to x = 0. The end members of the series were found to be isostructural with the ABW zeolite, LiAlSiO4-H2O, with space group Pc21n. The intermediate members of the serious either have the same ABW structure type, or crystallise in the space group P1211 with an ABW related structure consisting of phosphate tetrahedra and a combination of metal tetrahedra and square based pyramids. Thermal analysis in combination with variable temperature diffraction has shown that all members of the series undergo a phase transition at elevated temperatures. This structural change was investigated in detail for RbNi0.2Cu0.8PO4, which transforms at approximately 480°C to a phase isostructural with Polymorph 1 of CsZnPO4.
The synthetic aluminosilicate CsAlSi5O12, synthesised via a gel route, with the CAS framework type has been found to have a non-random distribution of aluminium across the three tetrahedral sites. A combination of high-resolution neutron diffraction and MASNMR has shown that the aluminium in the structure sits solely on the second of the three sites. The structure of the gallosilicate CsGaSi5O12 has been found to be isostructural with the CAS material. The structure based on X-ray diffraction shows a different distribution of gallium in the structure to that found for aluminium in CsAlSi5O12 with the majority of the gallium on the first and third tetrahedral sites.
A novel metal arsenate LiCoAsO4 has been synthesised and found to crystalline in the Pnma spacegroup. The material has a structure related to the olivine mineral, Mg2SiO4. Two isostructural metal arsenates, MM6’(OH)3(AsO4)(AsO4H) (M=M’=Co, Ni) have also been synthesised. The structures, determined from single crystal diffraction, show that the materials crystallise in the P63mc space group and are related to the mineral dumortierite. Both materials undergo a magnetic transition on cooling to a canted antiferromagnetic state. The new iron arsenate Fe7(HAsO4)4(AsO4)2, has been characterised as a three-dimensional network of arsenate tetrahedra linking iron octahedra and trigonal bipyramids. A piperazine arsenate material has been synthesised by a slow evaporation technique. The structure consists of a network of hydrogen bonded arsenate, water and piperazine groups.
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Published date: 2003
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Local EPrints ID: 465246
URI: http://eprints.soton.ac.uk/id/eprint/465246
PURE UUID: 3a3d13e2-4e39-4534-b555-4026ccf13a22
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Date deposited: 05 Jul 2022 00:31
Last modified: 16 Mar 2024 20:03
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Author:
Robert William Hughes
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