Crystallization and reaction kinetics of a crystallizable K_2O-CaO-SrO-BaO-B_2O_3-SiO_2 glass powder with 1-40 vol percent titania powder were investigated. The initially amorphous K_2O-CaO-SrO-BaO-B_2O_3-SiO_2 glass powder formed cristobalite (SiO_2) and pseudowollastonite (Ca, Ba, Sr)SiO_3 during firing. The above crystalline phases were completely replaced by a crystalline phase of titanite (Ca,Sr,Ba)TiSiO_5 when the amount of added titania was greater than a critical value, e.g., 10 vol percent, at 99-1100 deg C. A chemical reaction taking place at the interface between titania and the glass was attributed to the above observation. The dissolved titania changed the composition of the glass, and the dissolution kinetics was much faster than the formation of cristobalite and pseudowollastonite. Activation energy analysis showed that the crystallization of titanite (Ca,Sr,Ba)TiSiO_5 was controlled by a reaction-limiting kinetics of formation for the Ti-O bond.
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