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Structural and magnetic characterisation of some mixed metal oxides and oxyhalides

Stephens, Deborah Ann (2011)
Ph.D. thesis, University of Birmingham.

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Abstract

This thesis investigates the structural and physical effects of changing the ratio of Mn:Ga in the anion deficient perovskite, YSr\(_3\)Mn\(_{4-x}\)GaxO\(_{10.5}\). YSr\(_3\)Mn\(_{4-x}\)GaxO\(_{10.5}\) crystallises in the tetragonal space group I4/mmm, with lattice parameters a~7.64 Å and c~15.66 Å. Magnetic characterisation indicates that the material is antiferromagnetic overall, with ferromagnetic ordering in the [001] direction of the unit cell. Earlier work on the structural analogue, Y\(_{1.07}\)Sr\(_{2.93}\)Mn\(_{2.67}\)Ga\(_{1.33}\)O\(_{10.5}\), identified a magnetic peak in the neutron diffraction pattern that could not be fitted following refinement of NPD data. This work concluded that the extra peak was due to a small MnO impurity. The effects of oxidation and fluorination on the structural and physical properties of YSr\(_3\)Mn\(_{4-x}\)Ga\(_x\)O\(_{10.5}\) with various Mn:Ga ratios are investigated. The physical and structural effects of substituting Mn\(^{3+}\) or Co\(^{3+}\) for Fe\(^{3+}\) in the perovskite related material, Pb\(_4\)Fe\(_3\)O\(_8\)Cl, have been investigated using XRPD, NPD and magnetic susceptibility measurements. An earlier characterisation of Pb\(_8\)WO\(_{10}\)Cl\(_2\) suggested a deficit on all atom sites within the unit cell. This work suggests a different structure with an intact cation and main oxygen sub-lattice. The site of an additional oxygen was established linked to tungsten. Pb\(_8\)WO\(_{10}\)Cl\(_2\) crystallises in space group I4/mmm, with a = 3.9846(2) and c = 22.690(2) Å.

Type of Work:Ph.D. thesis.
Supervisor(s):Greaves, Colin (Professor)
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Subjects:TP Chemical technology
QD Chemistry
Institution:University of Birmingham
ID Code:1512
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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