Optical and analytical transmission-electron-microscopy studies of thermochemically reduced MgO crystals.

MgO crystals from five sources were thermochemically reduced at high temperatures. Optical-absorption measurements indicated that anion vacancies were present in all of the crystals. In addition, crystal darkening was observed and was due to a broad absorption in the visible region. The dark coloration was impurity related. Analytical transmission-electron-microscopy techniques indicated the presence of metallic precipitates that were primarily Fe in content. Microdiffraction patterns indicated that the precipitates possessed the fcc (a/sub 0/ = 3.61 A) or the bcc (a/sub 0/ = 2.89 A) crystal structure. The fcc precipitates were found to have a matrix relationship of /sub p/parallel /sub m/ and /sub p/parallel /sub m/. The bcc precipitates were found to have a relationship of /sub p/parallel /sub m/ and /sub p/parallel /sub m/.

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