Local atomic arrangement in amorphous aluminum oxide

Abstract

The local atomic arrangement of amorphous aluminum oxide is clarified by an electron diffraction study of anodic film formed in an aluminum-lead cell with a boric acid electrolyte. Diffraction patterns were produced in a Philips EM 300 electron microscope, tracings were made on a Joyce-Loebl densitometer and calibrated by the method of Karle and Karle. A reduced radial distribution and a radial distribution curve were prepared and partially interpreted by methods used by Vainshtein and also by Warren in X-rays. Ninety-two per cent of the aluminum atoms were found to be in tetrahedral configuration at 1.75Å separation distance and 8% in octahedral configuration at 1.85Å. Al-Al separations occur at 2.75Å and O-O separations at 3.20Å. The results agree qualitatively with a previous X-ray study by B. Burzlaff. In the present study more distant neighbor peaks were resolved although a complete model was not constructed. This study is the first application of radial distribution analysis of electron diffraction data to light atom structures containing two kinds of coordination polyhedra.