Electron diffraction study of inter‐ and intrapolytypic phase transitions in transition metal dichalcogenides. III. Complementary diffraction studies and lattice imaging of the deformation waves

Detailed electron diffraction results are given on the inter‐ and intrapolytypic phase transitions in tantalum disulfide and interpreted in terms of the transformation mechanisms involved. The orientation and spacing anomalies observed in the diffraction patterns are related to the incommensurate phases which are typical for the transition metal dichalcogenides. The complicated evolution of the electron diffraction patterns on going through the various transitions is analysed in detail. Anomalous diffraction spots could unambigeously be attributed to either partially transformed specimens and (or) double diffraction. By direct lattice imaging it is shown that the charge density waves and the associated deformation waves are static in nature. High resolution images of the incommensurate as well as the commensurate superstructures in NbTe₂, TaTe₂, and TaS₂ enable the direct visualisation of these deformation waves in electron microscopy.