Ferroelectric Properties and Crystal Structure of the Layered Intergrowth Phase Bi₃Pb₂Nb₂O₁₁Cl

Abstract

The crystal structure and physical properties of Bi3Pb2Nb2O11Cl, a member of the Sillen−Aurivillius phase intergrowth family, have been probed using powder neutron diffraction, high-resolution transmission electron microscopy (HRTEM), second harmonic generation (SHG) tests, and alternating current impedance methods. It is shown that this compound undergoes a diffuse ferroelectric type phase transition at T c ∼ 683 K. Although the powder neutron diffraction data show that the crystal structure has pseudo-tetragonal symmetry (parent space group P4/mmm, a p = 3.910 38(6) and c p = 18.8342(3) Å at 298 K), electron diffraction data clearly show a weak superlattice (a o ∼ b o ∼ (2)1/2 a p, c o = c p) compatible with a reduction of symmetry to orthorhombic, analogous to that observed in the related Aurivillius phases, such as SrBi2Ta2O9. Detailed analysis of the SHG data as a function of temperature suggests the existence of ordered polar nanodomains, compatible with the observation of “average” tetragonal symmetry in the neutron diffraction data. These observations, together with the presence of marked frequency dependence of T c, point toward a relaxor type ferroelectric behavior. The nature of the crystal structure, namely, a regular intergrowth of Aurivillius-like and Sillen-like blocks, [M2O2]/[MNb2O7]/[M2O2]/[Cl] [M = Bi, Pb], has been established from both Rietveld refinement of the powder neutron data and directly from HRTEM images. The observation of ferroelectricity in this material suggests the existence of a wider family of new ferroelectrics analogous to the Aurivillius phases.

Single Crystal Growth of Sillén–Aurivillius Perovskite Oxyhalides Bi4NbO8X (X = Cl, Br)

“…The single-crystal XRD on the platelet crystal revealed that a pseudo-merohedral twin is likely present with domains in the ab plane, in addition to the ferroelectric domains. We also report the growth of single crystal Bi 4 (n = 1, 2, 3, ...) constitutes a promising material platform not only for the photocatalysis but also for ferroelectric [24] or multiferroic properties [25]. We believe that the knowledge of single crystal growth obtained in this study on Bi 4 NbO 8 X can be applied to other Sillén-Aurivillius oxyhalide compounds.…”

Layered Intergrowth Phases Bi4MO8X (X=Cl, M=Ta and X=Br, M=Ta or Nb): Structural and Electrophysical Characterization

“…The #uorite-like block consists of fairly regular edge-sharing OBi tetrahedra, which are common to both SilleH n and Aurivillius phases, and also occur, for example, in the MOCuX family of complex oxides, oxyhalides and oxychalcogenides (15). The perovskite-like blocks in the present phases consist of a single octahedral MO layer which is markedly distorted, in contrast to that observed in the n"2 analog, Bi Pb Nb O Cl (9). These distortions are further discussed below.…”

“…Structurally, Bi NbO Br and Bi TaO Br display very similar distortions to their chloride analogs. It can be seen, for example, that the nature of the distortion of the MO octahedra is the same in each case *M is displaced o!-center towards a face of the octahedron rather than towards an apex, as is found in the A2X1 phase Bi Pb Nb O Cl (9). Also, the distortion around the Bi sites within the [Bi O ] layer is similar*the Bi> lonepair is stereochemically active in elongating the extra-layer Bi}X and Bi}O bonds, while the intra-layer Bi}O bonds remain short.…”

“…This series is represented by its simplest members Bi TaO Cl (A1X1, i.e., n"1, m"1), Bi Pb Nb O Cl (A2X1) (9) and Bi PbTi O Cl (A3X1) (7). We have recently shown that all of the above phases display ferroelectric properties, and have studied their properties and detailed crystallographic behavior of the ferroelectric phases by powder neutron di!raction (PND) (9,10).…”

Study of the sulfurized (BiO)2CO3 as efficient visible-light induced photocatalyst

“…A large number of semiconductor materials as photocatalyst have been developed, such as TiO 2 [2,3], ZnO [4][5][6][7], WO 3 [8,9], BiVO 4 [10][11][12], Bi 2 WO 6 [13,14] and BiOX [15][16][17][18][19][20][21]. However, the low photocatalytic efficiency and unfavorable chemical stability still hinders their practical application in elimination of the environmental hazardous contaminants.…”