Formation of celsian from mechanically activated BaCO3-Al2O3-SiO2 mixtures

A ternary mixture BaCO3-Al2O3-SiO2 was mechanically activated for different lengths of time. Chemical composition of the mixture corresponded to BaAl2 Si2O8-BAS As a function of activation time, reaction course was followed in the temperature range 750-1200 degrees C. Reaction of celsian formation wa s followed using thermogravimetry as well as conventional and high-temperat ure X-ray diffractometry. The obtained data show that reaction rate increas es with prolonged activation time, under the same conditions of thermal tre atment. Formation of hexacelsian via a series of solid state reactions invo lving Ba-silicates, was favoured with increasing activation time. Direct fo rmation of monoclinic celsian was retarded, however, with prolonged activat ion, (C) 1999 Elsevier Science S.A. All rights reserved.