Unusual High‐Temperature Structural Behaviour in Ferroelectric Bi₂WO₆

Abstract

The crystal structure of Aurivillius phase ferroelectric Bi2WO6 has been studied in detail as a function of temperature by using high-resolution powder neutron diffraction. In agreement with an earlier study, a transition from space group P2(1)ab to B2cb occurs at about 660 degrees C. This transition corresponds to the loss of one octahedral tilt mode within the perovskite-like WO4 layer of the structure. A second, reconstructive, phase transition occurs around 960 degrees C, corresponding to the ferroelectric Curie point; in contrast to previous suggestions, the structure of this high-temperature phase contains layers of stoichiometry WO4, with WO6 octahedra sharing edges and corners, and with the fluorite-like Bi2O2 layers remaining essentially unchanged. This structure is closely related to that of the ambient temperature phase of lanthanide-doped derivatives, for example, Bi0.7Yb1.3WO6 recently reported. This phase-transition behaviour is in stark contrast to that of other members of the Aurivillius family, such as SrBi2Ta2O9 and Bi4Ti3O12, which retain the archetypal Aurivillius connectivity at all temperatures.

First-principles study of the ferroelectric Aurivillius phase Bi2WO6

“…Experimental studies [13] showed that Bi 2 WO 6 is polar at ambient temperature with orthorhombic P 2 1 ab (No. 29) structure.…”

Phonon properties of nanosized bismuth layered ferroelectric material—Bi2WO6

“…[9,10] The room-temperature structure of Bi 2 WO 6 was refined using the P2 1 ab space group (the nonstandard setting of Pca2 1 was used in order to conform with the convention in Aurivillius phase ferroelectrics of assigning the long axis as c, and the polar axis as a), and it exhibits a second-order phase transition at 660 • C to the B2cb ferroelectric phase (nonstandard setting of Aba2) and a first-order phase transition at 960 • C to A2/m non-ferroelectric phase. [6] Recent studies showed that the photocatalytic properties of Bi 2 WO 6 depend on morphology and particle size. [10] It was shown for many materials that a change in the particle size may lead to significant structural changes: for instance, stabilization of the high-temperature phase, or even the appearance of new phases not observed for the bulk material.…”

Bi2WO6 Nanosheets Synthesized by a Hydrothermal Method: Photocatalytic Activity Driven by Visible Light and the Superhydrophobic Property with Water Adhesion

“…Zhang et al [11] synthesized porous Bi 2 WO 6 thin films, which possess high catalytic activity under visible light irradiation. McDowell et al [12] studied the Aurivillius phase ferroelectric Bi 2 WO 6 . Zhao et al [13] reported an electrospinning method to synthesize one-dimensional Bi 2 WO 6 nanofibers with an excellent visible photocatalytic property.…”