Unusual high-temperature structural behaviour in ferroelectric Bi2WO6.

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Aurivillius phase ferroelectrics, such as Bismuth Tungstate (Bi2WO6), are crucial materials in electronic applications.
• Understanding their structural behavior under varying temperatures is key to optimizing their properties.
• Previous studies have suggested certain transition behaviors, necessitating further investigation.

Purpose of the Study:

• To elucidate the temperature-dependent crystal structure of Aurivillius phase ferroelectric Bi2WO6.
• To precisely identify the structural changes and phase transitions occurring at elevated temperatures.
• To compare the phase transition behavior of Bi2WO6 with other Aurivillius family members.

Main Methods:

• High-resolution powder neutron diffraction was employed to study the crystal structure.
• The study systematically analyzed the material's structure across a range of temperatures.
• Data was collected and analyzed to determine space groups and structural motifs.

Main Results:

• A phase transition from space group P2(1)ab to B2cb was observed around 660°C, linked to the loss of an octahedral tilt mode.
• A second, reconstructive phase transition occurred near 960°C, identified as the ferroelectric Curie point.
• The high-temperature phase features WO4 layers with edge- and corner-sharing WO6 octahedra, distinct from previous assumptions and similar to lanthanide-doped derivatives.

Conclusions:

• Bi2WO6 exhibits distinct phase transition behavior compared to other Aurivillius compounds like SrBi2Ta2O9 and Bi4Ti3O12.
• The identified structural changes provide critical insights into the ferroelectric properties of Bi2WO6.
• The findings contribute to a deeper understanding of structure-property relationships in Aurivillius ferroelectrics.