The structure and ferroelectric properties of layered compounds in the system Bi4Ti3O12Bi2WO6

Abstract

Numerous layered compounds are found to exist in the system Bi4Ti3O12–Bi2WO6. Many of them have the mixed‐layer structures built up as ordered stackings of perovskite‐like fragments of different thickness interleaved with Bi2O2‐sheets, which can be described by a general formula (Bi2O2) (Am−1BmO3m+1)(Bi2O2)(An−1BnO3n−1). Single crystals of two these compounds, Bi6Ti3WO18 and Bi10Ti3W3O30, are grown and proved to be ferroelectric with the Curie points 750 and 735 °C, respectively. In conclusion, some peculiarities of symmetry and phase transitions of similar layered crystals are discussed.

Crystal Structure and Phase Transition in the Defect Pyrochlore NH4NbWO6

“…This class of compounds exhibits many interesting physical properties such as ferroelectricity and fast ionic conductivity (2)(3)(4), which make some of them suitable choices for applications in fuel cells and other similar devices. Among them, several defect pyrochlores AB O (5) (where A is, e.g., H, NH , Rb, Cs, Cd, K, Na, or Tl and B is a small cation, e.g., Nb, W, Ta, Te, Sb, or V) have been studied by many different experimental techniques, including X-ray and neutron diffraction, inelastic neutron scattering, Raman and infrared spectroscopy, thermal analysis, impedance spectroscopy, NMR, and second-harmonic generation, leading in some cases to a successful understanding of their physical properties in terms of particular features of their crystal structures (see, e.g., (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)).…”

Crystal structure of the ‘mixed-layer’ Aurivillius phase Bi5TiNbWO15

“…46); since this material is known to be ferroelectric at room temperature, the latter (polar) space group was assumed in subsequent analysis. In fact, two teams had previously predicted this space group for an Aurivillius phase of the (n ¼ 1; 2) type, using quite different approaches [10,16]. The (n ¼ 2; 3) phase Bi 7 Ti 4 NbO 21 was also found to adopt this space group (with c $ 58 ( A), and a starting model for the present structure could easily be derived from this, by appropriate adjustments.…”

Structure–property correlations in the new ferroelectric Bi5PbTi3O14Cl and related layered oxyhalide intergrowth phases

“…38). Moreover, this space group had also been suggested as an ideal model for a 'mixed odd-layer' Aurivillius phase of the type A1A3, 15 which might be expected to be architecturally similar to the present phase. Refinement of the structure at 25 uC was therefore carried out in this space group using a model derived from that of Aurivillius in C2mm.…”