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, th e influence of nucleating agents such as TiO2, ZrO2, Cr2O3, and Ni on MgO b ase glasses was elucidated. The glasses are of interest for the development of sealants in Solid Oxide Fuel Cells (SOFC). The activation energy of cry stal growth, E-a, was evaluated for the different glasses using the modifie d Kissinger equation. The preparation method of the glasses seems to determ ine whether surface or bulk nucleation is the dominant mechanism. The E-a v alues vary between 330 and 622 kJ/mol. The nucleating agents tend to enhanc e E-a except ZrO2. An increase of the Al2O3 concentration induces phase sep aration and decreases E-a. The results are discussed on the basis of the st ructural role and chemical properties of the Al ions as well as with respec t to the possible use of the glasses in SOFC. (C) 2000 Kluwer Academic Publ ishers.