Sintering Kinetics of an Yttrium Aluminosilicate Glass

ABSTRACTYttrium aluminosilicate (YAS) glasses have been proposed as host matrices for the immobilization of radioactive elements. In addition, yttrium has been used to simulate actinides [1]. It is well known that these glasses are resistant to water corrosion and exhibit high Tg and good mechanical properties [2]. As shown in [3], on heating, yttrium disilicate and mullite / sillimanite crystals grow from the pre-existing nucleation sites on the surface, until each glass particle volume is fully crystallized (volume-homogeneous nucleation was not observed), decreasing the glassy surface available for sintering by viscous flow. Sintering takes place simultaneously, by viscous flow but competes with surface crystallization; thus, if thermal treatment is not carefully designed a vitroceramic is obtained. In this paper we study the isothermal sintering kinetics of a YAS glass-powder-size distribution and non-isothermal sintering kinetics at 1, 3, 5, 10 and 15 K/min of two YAS glass-powder-size distributions. From the experimental evidence obtained, and crystallization data from [3], we design a sintering procedure in order to achieve a high-density glass monolith with submicrometric crystalline phases.