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

The crystal structure of the Aurivillius phase Bi5TiNbWO15 has been analyzed in detail using powder X-ray and neutron diffraction. The structure can be described as a regular intergrowth of alternating single and double perovskite-like layers sandwiched between fluorite-like bismuth oxide layers, such that the layer sequence is … [WO4]–[Bi2O2]–[BiTiNbO7]–[Bi2O2] …. There is complete ordering of tungsten within the B sites of the single perovskite layer, so that the structure can be described as a direct intergrowth of the ‘component’ Aurivillius phases Bi2WO6 and Bi3TiNbO9. At 25 °C the structure adopts the polar orthorhombic space group I2cm, image, image, image.