The high-temperature transformation of andalusite (A12SiOs) into 3/2-mullite (3A12Oa2SiO2) and vitreous silica (SiO2)
نویسنده
چکیده
S U M M A R Y . The high-temperature transformation of andalusite (AI2SiOs) into 3/2-mullite (3AIzO32SiO2) plus vitreous silica (SiO2) has been studied within the temperature interval from 13oo to 16oo ~ by means of X-ray powder and single-crystal techniques and by infrared spectroscopy. Results are interpreted in terms of a topotactic transformation in which (oi I) and (oI i) planes of andalusite transform into (2oi) and (20 I) planes of 3/2mullite; in this way the aand b-axes of the two phases are interchanged. From the structural and orientational relationship between the andalusite and 3/2-mullite latrices it is concluded that the aluminium-oxygen octahedral chains, running in both structures parallel to the crystallographic c-axis, are preserved during phase transformation.
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