Crystallisation kinetics in AO-Al2O3-SiO2-B2O3 glasses (A = Ba, Ca, Mg)

The crystallisation kinetics of AO-Al2O3-SiO2-B2O3 glasses (A = Ba, Ca, Mg) was investigated using DTA, XRD, and microstructural studies. Moreover, the influence of nucleating agents such as TiO2, ZrO2, Cr2O3, and Ni on MgO base glasses was elucidated. The glasses are of interest for the development of sealants in Solid Oxide Fuel Cells (SOFC). The activation energy of crystal growth, E-a, was evaluated for the different glasses using the modified Kissinger equation. The preparation method of the glasses seems to determine whether surface or bulk nucleation is the dominant mechanism. The E-a values vary between 330 and 622 kJ/mol. The nucleating agents tend to enhance E-a except ZrO2. An increase of the Al2O3 concentration induces phase separation and decreases E-a. The results are discussed on the basis of the structural role and chemical properties of the Al ions as well as with respect to the possible use of the glasses in SOFC. (C) 2000 Kluwer Academic Publishers.