VPI-5 transforms to AlPO4–8 under mild thermal treatment (100 °C, 18 hrs). HRTEM micrographs, oriented normal to the c axis, show extensive defect-free regions in VPI-5, while slip planes normal to the c axis are found in AlPO4–8. Analysis of the HRTEM data, in conjunction with infrared and thermal analysis, adsorption studies and x-ray powder diffraction, has lead to a proposed structure for AlPO4–8. Though the sheets containing the 18 member rings which define the pores in VPI-5 remain intact in AlPO4–8, reduction in the porosity is attributed to blockages created by the movement of these sheets relative to each other.

A number of examples of high resolution electron microscopy on defects and metal particles in zeolites is given: defects in Zeolite Y and Zeolite β, metal particles in ZSM-5, and structural changes due to reactions in Zeolite L and Zeolite Y.

High resolution electron microscopy observations were carried out in several zeolitic systems with different supported metallic phases in order to determine besides distributions of metallic particles, possible preferential orientations of metallic phases during impregnation processes and to detect some crystallographic relations between metallic particles and support.

A review is given of defects occurring in the superconducting oxides YBa2Cu3O7, (Bi,Tl)2(Sr,Ba)2CanCul+nO6+2n, and Pb2Sr2(Cal-xYx)nCu2+nO6+2n+∂. A number of these defect structures correspond to other thermodynamically stable phases. The observations of these defects have led in several cases to successful synthesis of new superconducting compounds. Defects can effect the superconducting properties, which they can either deteriorate (weak links) or improve (flux pinning). Both effects are considered.

Intensity fluctuation in high resolution electron microscope (HREM) images of amorphous Tl-Ba-Ca-Cu-O oxide films is observed. The fluctuation with a frequency of few tens of Hertz and an amplitude of about 0.3nm, occurs under an intense electron beam irradiation. It is shown experimentally that atom migration in the films is responsible for the fluctuations. The result is also supported by computer image simulations on a model structure for amorphous film.

Thin films of YBa2Cu3O7 have been prepared by evaporation of Cu, Y and BaF2 onto (001) SrTiO3, LaGaO3. and LaAlO3 and subsequent annealing. Their microstructures have been examined by HREM of cross-sectional specimens. Epitaxial (001) grains of YBa2Cu3O7 form near the substrate interface in thin films but (001) and (010) grains tend to nucleate as the film thickens. 90° grain boundaries are therefore common, as well as other defects such as small-angle boundaries, dislocations and stacking faults. HREM of the substrate/superconductor interface indicates regions of perfect epitaxy, highly distorted areas, amorphous regions and areas showing evidence of interdiffusion. The relationship of these microstructural features to critical current density is discussed.

Transmission Electron Microscopy has been used to study the morphology and defect structure of sharp superconducting transition, high (2-6 ×107 A/cm2) critical current YBa2Cu3O7−δ films on MgO substrates. These were oriented such that the unit cell axes of the film aligned with those of the substrate, with some domains obeying a second orientation relationship rotated by 45° in the plane of the film, i.e. film <110> parallel to substrate <100>. The latter is not expected from simple lattice matching considerations. A strong influence of substrate surface topography on film microstructure was noted, leading to a high density of out-of-phase, low-angle tilt, and other boundaries near the substrate-film interface, which decreased with increasing distance from the substrate. Finally, the effects on film microstructure of two variables of specific interest in our sputtering system were investigated: the thickness of the deposited film, and the temperature at which a high oxygen pressure (500 torr) is introduced after deposition is complete. Increases in film thickness resulted in longer, more widely spaced twins, whereas lower oxygenation temperatures resulted in shorter twins.

High resolution electron microscopy is used to investigate the effect of electron irradiation induced oxygen loss on the states of partial order in YBa2Cu3Oz. Contrast effects visible in the [001] zone image as a result of the degree of the out-of-plane correlation of these ordered states are investigated. Using statistical simulations to aid in the analysis of the HREM images, an interpretation based on a kinetically limited evolution of the variation of long range [001] ordering is proposed.

Mechanial deformation of the YBa2Cu3O7−δ high temperature superconductor under a number of different processing conditions resulted in the formation of <100> and <110> edge dislocations, both having a (001) slip plane. Subsequent high temperature annealing at 900°C resulted in the formation of extrinsic stacking faults with a large separation of the partial dislocations, up to 0.35 μm, suggesting a very low minimum stacking fault energy of 1.2 × 10−2 J/m2. High resolution transmission electron microscopy (HRTEM) in conjunction with image simulations revealed that the stacking faults were comprised of an extra CuO plane between the Ba layers with an offset of b/2. The stacking fault vector of 1/6[031] requires some separation of the <010> Burgers vectors into the c-axis direction. A model in which [010] separates into 1/6[031] + 1/[031] is consistent with the observed stacking faults.

We have studied the micro-structure of shock synthesized Tl2Ba2CuO6, shockprocessed YBa2Cu3O7 and 10% Ag-YBa2Cu3O7. The structural interpretation of the defects observed in these materials is discussed and compared with computer simulated images. Two planar defects with a stacking sequence of Cu-Ba-Tl-Ba-Cu and Cu-Ba-Tl-Tl-Ba-Cu-Tl-Cu-Ba-Tl-Tl-Ba-Cu in the Tl based oxide and a new defect sequence of Cu-Ba-Cu-Y-Y-Cu-Ba-Cu in the Y based oxides are reported here. An attempt is made to relate the change in superconducting properties observed to the defect structure present.