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Synthesis and characterisation of materials with potential multiferroic behaviour

D'Souza, Rhys (2010)
M.Res. thesis, University of Birmingham.

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Abstract

The ceramic method was used to produce Aurivillius phase materials, B i \(_3\)NbTiO\(_9\) and Bi\(_4\)Ti\(_3\)O\(_1\)\(_2\). Unit cell structures have been determined to be of A2\(_1\)am and Fmmm symmetry, respectively. In addition, the fractional co-ordinates of the constituent atoms has been calculated by Rietveld refinement. A range of materials of general formula Bi\(_5\)Fe\(_1\)\(_+\)\(_x\)Ti\(_3-x)\O\(_1\)\(_5\) was produced with a value of x ranging from 0 to 2.5, which is higher than reported. Attempts to produce Bi\(_5\)Fe\(_4\)O\(_1\)\(_5\), with all the Ti\(^4\)+ sites occupied by iron atoms proved unsuccessful. The space group of Bi\(_5\)FeTi\(_3\)O\(_1\)\(_5\) was determined to be A2\(_1\)am, however, the other 4-layer bismuth phases proved difficult to characterise without more data. Increasing the number of pseudo-perovskite layers from 2 to 3 to 4 (Bi\(_3\)NbTiO\(_9\) to Bi\(_4\)Ti\(_3\)O\(_1\)\(_2\) to Bi\(_5\)FeTi\(_3\)O\(_1\)\(_5\)) had a notable effect in increasing the unit cell size along the z-axis, going from c=25.192(1)Å to c=32.785(1)Å to c = 41.179(1). The magnetic properties of Bi\(_5\)FeTi\(_3\)O\(_1\)\(_5\), Bi\(_5\)Fe\(_2\)Ti\(_2\)O\(_1\)\(_5\) and Bi\(_5\)Fe\(_3\)TiO\(_1\)\(_5\) have been recorded, as part of an attempt to find multiferroic materials. The information collected would suggest that Bi\(_5\)FeTi\(_3\)O\(_1\)\(_5\) and Bi\(_5\)Fe\(_3\)TiO\(_1\)\(_5\) display some anti-ferromagnetic behaviour, whereas Bi\(_5\)Fe\(_2\)Ti\(_2\)O\(_1\)\(_5\) appears to be a paramagnet. Failure to produce Bi\(_5\)MnTi\(_3\)O\(_1\)\(_5\) , by other researchers methods, raises doubts about manganese substitution into the bismuth-layer structure.

Type of Work:M.Res. thesis.
Supervisor(s):Greaves, Colin (Professor)
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:Chemistry
Subjects:QD Chemistry
Institution:University of Birmingham
ID Code:357
This unpublished thesis/dissertation is copyright of the author and/or third parties.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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