Electron microscopy observations of the incommensurate phase in berlinite and quartz : interference contrast in the c-zone axis conditions

Publisher Website
Google Scholar
Abstract
The triply modulated incommensurate phase of berlinite and quartz is imaged by electron microscopy in c-zone axis orientation conditions. The systematic study of the images and of the incommensurate diffraction satellites shows that the apparently triangular dark/light contrast pattern obtained with the transmitted beam or a general hk0-reflection and the surrounding satellites can be explained by an interference contrast model similar to that for usual high resolution lattice imaging. This interference image is consistent with the phase relation of the triple incommensurate modulation conjectured by the minimisation of the free energy, according to the existing theoretical work