Experiments in high-voltage electron microscopy. Final report for the period ending November 30, 1982

This final report summarizes the achievements of the past ten years of DOE support of research on high voltage electron microscopy. The most notable accomplishments have been in the area of radiation damage, particularly in metallic alloys and ceramic compounds. For the case of substitutional alloys it has been shown that enhanced precipitation can occur for supersatured solutions, while undersaturated solid solution alloys can also be de-stabilized by irradiation, leading to either homogeneous or heterogeneous precipitation; heterogeneous sites include foil surfaces. Ordered compounds have also been studied extensively and it has been shown that the point defects generated can lead to disordering at low temperatures or secondary defect formation (dislocation loops) at higher temperatures. The behavior of ceramics divides sharply into those like quartz which undergo ionization damage leading to amorphization and those like MgO and Al2O3 which undergo normal knock-on damage leading to secondary defect formation (loops and voids). Microstructures of a wide-range of ceramics (e.g. YAG, Si3N4, MgAl2O4) have been studied and related to their crystal structures. Other important discoveries have been the influence of grain boundaries where the microstructural development is different and could lead to enhanced degradation