QUANTITATIVE-ANALYSIS OF HREM IMAGES OF ALPHA-ALB12 WITH A HIGH-VOLTAGE TRANSMISSION ELECTRON-MICROSCOPE AND THE IMAGING PLATE

High-resolution electron microscope images of alpha-AlB12 were quantit atively observed by using a high-voltage transmission electron microsc ope and the new Imaging Flare having a pixel size of 25 mu m. in order to quantitatively evaluate the difference between the observed intens ity and the calculated one, a residual index R-HREM which indicates th e accuracy of a calculated image was evaluated for 1440 sampling point s in the unit cell projected along the [111] direction. The residual i ndex R-HREM of 0.0576 was obtained with the averaged high-resolution e lectron microscope image and the calculated image based on the structu re model obtained from the X-ray diffraction study. In the observed hi gh-resolution electron microscope image, some regions had extraordinar ily higher intensity than other regions which were crystallographicall y equivalent to the regions. In a quantitative analysis of the observe d images including those regions, the minimum R-HREM at 0.0738 was obt ained by varying the occupancy of Al atoms although the R-HREM remarka bly increased from the minimum value obtained in the quantitative anal ysis of the averaged image. The effects of a contamination layer cover ing the sample on the above quantitative analysis of high-resolution e lectron microscope images are briefly discussed.