Role of mineralizers on the hexacelsian to celsian transformation in the barium aluminosilicate (BAS) system

The mechanism of additive-enhanced kinetics of the hexacelsian-celsian transformation in BAS was assessed by doping various mineralizers having different cationic radii and valence. The semi-quantitative data of XRD analysis indicate that an ionic valence of +3 is less efficient and ionic radii ranging from 0.68 to 1.12 are more effective in promoting celsian formation. Insights about the sites in which the doped cations reside are obtained by examining the possible defect structures developed in the mineralizer-containing hexacelsian. Oxygen- and barium-vacancies defects induced by the addition of mineralizers in BAS could assist the breaking of Ba-O or (Al, Si)-O bonds and promote the polymorphic transformation. 2002 Elsevier Science B.V. All rights reserved.