In situ X-ray diffraction studies of deformation behavior of ferroelectric triglycine sulfate under uniaxial compression

A combination of high-resolution X-ray diffraction and X-ray diffraction topography was used for analysis and visualization of elastic strain in ferroelectric triglycine sulfate (TGS) single crystals under uniaxial compression. Diffraction peaks and topographs were obtained for both the 400 and 060 reflections of TGS in transmission geometry under gradually increased compression stress up to 3.5 MPa applied along the [100] and [010] crystallographic directions. All the diffraction data from the sample were obtained from the whole crystal volume with wide beam illumination. Analysis of diffraction patterns revealed a nonlinear increase in integral intensity versus stress and a linear increase in peak broadening versus stress for all compression measurement combinations. The topographs confirmed that the formation of uniform and non-uniform strain fields depended on the direction of crystal compression and its relationship with integral intensity. A twinning process was found for the in-plane reflection along the [100] direction. All the effects induced by compression were reversible after decompression of the sample. According to the results, a significant anisotropy of deformation processes depending on the crystallographic direction was observed, which can be explained by the proposed deformation mechanism with superposition of compression stress, the piezoelectric effect and ferroelectric domain evolution.