Kinetics of Ag distribution in high lead glass by real time synchrotron powder diffraction

In the present work we studied the time-temperature behaviour of Ag dispersed in high lead glass layers printed on an 96% alumina substrate. The inks used for the samples were prepared from glass, silver powders and an organic vehicle. The kinetic mechanism of Ag dissolution in the glassy matrix has been investigated by synchrotron XRPD (at beamline 2.3, Daresbury Laboratory, UK) in isothermal conditions. The behaviour versus firing temperature of fine Ag grains dispersed in the thick film dielectric has been investigated by SEM, SEM-EDS and conventional XRD. The kinetic analysis shows an Avrami-like dissolution mechanism: the order of the reaction n is in the range 2.3÷3.7. There is a small but significant decrease of n with temperature. The change could be related to faster heat motion so that the reaction is favoured. The calculated apparent activation energy is 16(1) kcal/mole. The SEM-EDS and XRD analyses show a characteristic floating of Ag as the firing temperature changes.