Structural Behavior of the Four-Layer Aurivillius-Phase Ferroelectrics SrBi4Ti4O15 and Bi5Ti3FeO15

✍ Scribed by Charles H. Hervoches; Alan Snedden; Richard Riggs; Susan H. Kilcoyne; Pascal Manuel; Philip Lightfoot

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 460 KB
• Volume: 164
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9473

✦ Synopsis

Rietveld refinement of powder neutron diffraction data has been used to study the crystal structures of the four-layer Aurivillius-phase ferroelectrics Bi 5 Ti 3 FeO 15 (at 251C) and SrBi 4 Ti 4 O 15 (at a series of temperatures up to 8001C). At 251C both materials adopt the polar orthorhombic space group A2 1 am, in common with two-layer analogues such as SrBi 2- Ta 2 O 9 . At temperatures well above the ferroelectric Curie temperature (i.e., at temperatures of 6501C and above, with T c B5501C) SrBi 4 Ti 4 O 15 transforms to the centrosymmetric tetragonal space group I4/mmm. However, there is good evidence from the raw diffraction data of a very subtle intermediate paraelectric orthorhombic phase, of Amam symmetry, in the region 55046501C. The distortion in the ferroelectric phase can be traced to displacements of the cations in the A site of the perovskite block, with cooperative tilting of the BO 6 octahedra. The nature of the octahedral tilt system, cation disorder at the perovskite A and B sites, and the phase transition sequence in SrBi 4 Ti 4 O 15 , which parallels that found in SrBi 2 Ta 2 O 9 , are discussed.