Transition of V₆O₁₃ to VO₂ observed with a high-resolution electron microscope

Under irradiation by an intense electron beam a V₆O₁₃ crystal reacts with the carbon deposited on the surface during microscopic observation. The structural changes during the reaction were directly observed by means of lattice images, in which the array of VO₆ octahedra was resolved. At the initial stage cavities smaller than 20 Å in diameter appear preferentially in the thin part of the crystal and some crystallographic shear planes are formed in their wall. The cavities with the heavily distorted surroundings are seen as white regions. Kinks in lattice fringes, indicating the occurrence of stacking faults, are simultaneously found in the matrix. At the advanced stage the VO₂ phase and its twin component are produced. The mechanism of the transition of V₆O₁₃ to VO₂ can be interpreted in terms of the cooperative movement of octahedra.