CRYSTALLIZATION OF PRECURSORS TO FORSTERITE AND CHROMIUM-DOPED FORSTERITE

The pyrolysis and crystallization of poly(methacrylate) precursors and xerogels of forsterite and chromium-doped forsterite were studied by in situ high-temperature, dynamic X-ray diffraction and thermal analys is. For both types of precursor, crystallization of forsterite occurre d at lower temperature when doped with chromium. Also, exotherms above 700-degrees-C occurred 50-degrees-C lower when chromium was present. When residual carbon in the xerogels was more than approximately 1%, a n unidentified crystalline intermediate phase formed at approximately 800-degrees-C. Conversion of the intermediate phase to forsterite was faster than amorphous material. Thus, full crystallinity was attained at a lower temperature when the xerogels had some residual carbon.