Unusual High‐Temperature Structural Behavior in Ferroelectric Bi₂WO₆.

Abstract

Structure D 2000Unusual High-Temperature Structural Behavior in Ferroelectric Bi 2 WO 6 . -The crystal structure of the title compound is characterized by high-resolution powder neutron diffraction as a function of temperature. A transition from space group P21ab to B2cb occurs at about 660°C and a second transition to space group A2/m around 960°C. The structure of this high-temperature phase contains layers of stoichiometry WO 4 , with WO 6 octahedra sharing edges and corners, and the fluorite-like Bi 2 O 2 layers remaining essentially unchanged. This phase-transition behavior is in contrast to that of other members of the Aurivillius family, such as SrBi2Ta2O9 and Bi4Ti3O12, which retain the archetypal Aurivillius connectivity at all temperatures. -(MCDOWELL, N. A.; KNIGHT, K. S.; LIGHTFOOT*, P.; Chem. Eur.

Piezoelectric and Ferroelectric Properties of Bismuth Tungstate Ceramics Fabricated by Spark Plasma Sintering

“…Bi 2 WO 6 is the simplest member ( m =1) of the BLSFs family, and has a high Curie point (above 900°C). At room temperature, Bi 2 WO 6 has the orthorhombic space group P 2 1 ab , 6,7 and not B 2 cb as reported in earlier work, 8 with a =5.457 Å, b =5.436 Å, and c =16.427 Å. In addition to the paraelectric–ferroelectric phase transition, Bi 2 WO 6 ceramics have been suggested to have a second phase transition in the temperature range from 600° to 700°C, accompanied by changes in lattice parameters, but their structure remains orthorhombic 7,9 .…”

“…At room temperature, Bi 2 WO 6 has the orthorhombic space group P 2 1 ab , 6,7 and not B 2 cb as reported in earlier work, 8 with a =5.457 Å, b =5.436 Å, and c =16.427 Å. In addition to the paraelectric–ferroelectric phase transition, Bi 2 WO 6 ceramics have been suggested to have a second phase transition in the temperature range from 600° to 700°C, accompanied by changes in lattice parameters, but their structure remains orthorhombic 7,9 . However, the Curie point and phase transition temperatures reported in the literature are inconsistent 6,8,10,11 .…”

“…Pure Bi 2 WO 6 has the P 2 1 ab orthorhombic structure with the polarization along the a ‐axis at room temperature and a phase transition to the A 2/ m monoclinic space group above Curie point 7 . Based on the atomic displacements, the total P s of the displacive‐type ferroelectric Bi 2 WO 6 can be calculated using Shimakawa's model 18 where m i is the site multiplicity, Δ x i is the atomic displacement along the a ‐axis from the corresponding position in the monoclinic structure, Q i e is the ionic charge of the i th constitute ion, and V is the volume of the unit cell.…”

“…In addition to the paraelectricferroelectric phase transition, Bi 2 WO 6 ceramics have been suggested to have a second phase transition in the temperature range from 6001 to 7001C, accompanied by changes in lattice parameters, but their structure remains orthorhombic. 7,9 However, the Curie point and phase transition temperatures reported in the literature are inconsistent. 6,8,10,11 Bi 2 WO 6 has been considered as a high-temperature piezoelectric materials because of its high Curie point and the high piezoelectric coefficients of single crystals (d 33 B40 pC/N).…”

Low temperature synthesis of Bi2WO6 and its photocatalytic activities

“…In recent years, bismuth-based catalysts as a new type of photocatalytic materials have become a hot topic in the photocatalysis research field, especially for the photocatalytic degradation of pollutants using visible light [10][11][12]. Kudo [13][14][15][16]. Because of the strong correlation between photocatalytic activity and parameters such as surface area, structure, efficiency of electron-hole separation and the particle diameter of photocatalysts [17], great interest have been focused on controlling the shapes and discovering novel properties of nanostructured materials [18].…”