Sintering of glasses in the system RO-Al2O3-BaO-SiO2 (R=Ca, Mg, Zn) studied by hot-stage microscopy

Glass-ceramics for sealing solid oxide fuel cells (SOFCs) were developed by sintering and crystallization of the powdered glass seal. The non-isothermal sintering kinetics and crystallization kinetics were studied for four glasses in the system 50SiO(2)(.)(45 - x)BaO(.)xRO(.)5Al(2)O(3) (R = Ca, Mg, Zn and x = 0, 15) (mol%). Hot-stage microscopy (HSM) and differential thermal analysis (DTA) measurements demonstrated that it is possible to first sinter and then crystallize these glasses obtaining glass-ceramic seals with thermal expansion coefficients in the range 9-12 x 10(-6) K-1. The non-isothermal sintering kinetics was analyzed by computer simulations using a previously reported model of sintering for polydispersed glass powders which takes into account the particle size distribution, surface energy and viscosity. Good agreement was found between the measured kinetics with HSM and the calculated kinetics for all glasses. (C) 2004 Elsevier B.V. All rights reserved.