Formation of crystalline silicon in kaolinite by electron beam irradiation and in situ heating in the HVEM.

Electron beam irradiation can change the bulk structure of a specimen permanently. The crystallizations of amorphous phases in the 900 degrees C-heated kaolinite by electron beam irradiation and natural kaolinite by in situ heating are observed in a 1250 keV HVEM in this study. Crystalline silicon was formed in both cases. The lack of the parent structure and the aluminum loss are obstacles to the formation of the spinel-type phase. Amorphous silica is segregated instead and silicon crystals are progressively formed through Si--O bond breakage and Si--Si bond formation. Irradiation damage and element loss are considered to contribute to the crystallization of silicon under ultra high vacuum.