Transmission-electron-microscopy observation of the memory effect through the pattern of discommensurations in barium sodium niobate

Abstract

We report the first observation in direct space of a manifestation of the memory effect specific to incommensurate (INC) materials. It is found, using transmission electron microscopy, that barium sodium niobate samples cooled rapidly after annealing in the INC phase exhibit at room temperature two distinct regions with different configurations and spacings of discommensurations. These results are correlated to x-ray diffraction data.