Real-Time atomic-level observations of in situ chemical reactions and transformations utilizing high-resolution electron microscopy

Three studies ofin situ chemical reactions or transformations utilizing real-time video recording of high-resolution microscopic images to reveal atomic resolution details are reported. In one study, the removal of a twin plane separating a surface promontory consisting of several hundreds of atoms from the main body of a TbO_x crystal is observed. In another study of a leached TbO_x specimen, the decomposition of a Tb(OH)₃ surface impurity is followed as the oxide product is accreted to the main body of the TbO₂ crystal. In a third example, a crystal of modified PbO2 grown from acid solution displays, in high resolution, rapid cooperative movement of scores to hundreds of atoms over the crystal surface before finally decomposing, presumably with loss of hydrogen, toβ-PbO₂. This paper is based on a presentation made in the symposium “The Role of Ledges in Phase Transformations” presented as part of the 1989 Fall Meeting of TMS-MSD, October 1–5, 1989, in Indianapolis, IN, under the auspices of the Phase Transformations Committee of the Materials Science Division, ASM INTERNATIONAL.