New intergrowth Bi2WO6-Bi3TaTiO9 ferroelectrics

A new intergrowth bismuth layer-structured ferroelectric, Bi2WO6-Bi3TaTiO9 (BW-BTT), was successfully synthesized by solid-state reaction, and the reg ular intergrowth structure was confirmed by the Rietveld method. Differenti al thermal analysis measurements suggested that the BW-BTT underwent ferroe lectric phase transitions twice at around the Curie temperatures of the con stituent compounds of BW and BTT. The structural analysis of the BW-BTT sho wed that there are two kinds of Bi ions in the bismuth oxide layers, and th at one Bi ion was displaced to the polarization direction by about 2% of th e lattice constant a from the corresponding position in the parent tetragon al structure. This displacement of Bi in the bismuth oxide layers is the st ructural feature which was found for the first time for both conventional a nd intergrowth bismuth layered structures.