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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. Greaves, Colin (Professor) Colleges (2008 onwards) > College of Engineering & Physical Sciences Chemistry QD Chemistry University of Birmingham 357
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