Synthesis, structure and characterisation of the n=4 Aurivillius phase Bi 5Ti 3CrO 15

Abstract

The n=4 Aurivillius phase, Bi 5Ti 3CrO 15, was synthesised by solid state reaction. Rietveld analysis of high resolution neutron diffraction data demonstrated this material to adopt the polar space group A2 1 am at room temperature, transforming to the aristotype I4/ mmm structure above 650 °C. This phase transition is coincident with an anomaly in DSC signal and relative permittivity, which are characteristic of a ferroelectric–paraelectric phase transition. Bi 5Ti 3CrO 15 exhibits paramagnetic behaviour at low temperature, with short range antiferromagnetic interactions, but no evidence for long range magnetic ordering. This is considered a consequence of significant disorder of Ti and Cr over the available octahedral sites, as demonstrated by analysis of neutron diffraction data.