Synthesis and characterisation of materials with potential multiferroic behaviour

D'Souza, Rhys (2010). Synthesis and characterisation of materials with potential multiferroic behaviour. University of Birmingham. M.Res.

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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:

Thesis (Masters by Research > M.Res.)

Award Type:

Masters by Research > M.Res.

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