Study of Near-Surface Local Structural Change on Thermal Behavior of Forsterite Precursor by XANES Spectroscopy
Takushi MINAGI, Takeshi SHIONO, Hirofumi ARITANI and Toshihiro NISHIDA
Abstract:Forsterite (Mg2SiO4) precursor was synthesized from heterogeneous alkoxide solution containing MgO powder (mean particle size : 10nm). In order to examine thermal behavior of the precursor, DTA was carried out. The precursor was calcined at temperatures before and after each exothermic and endothermic reaction. The calcined powders were examined by XRD analysis and FT-IR spectroscopy to clarify the reactions. It was found that C2H5OH adsorbed on the surface of the powder evaporates at 82, Mg(OH)2 decomposes at 390 and that forsterite phase is formed at 796. The changes in near-surface crystal structure involving these reactions were evaluated by Si and Mg K-edge XANES spectroscopy. The forsterite precursor was found to have a metastable structure before crystallizing as forsterite crystal, resulting from the dehydration around 400. The phase was identified as amorphous and the electronic structure was close to Mg2Si3O8. Key Words:Forsterite precursor, alkoxide method, Si K-edge XANES, Mg K-edge XANES, Near-surface local structure