Effect of devitrification on the ionic diffusion of Li-disilicate

Effect of devitrification on ion motion in lithium-disilicate glass

“…The analysis of the micrographs yielded the time (and temperature) dependence of volume fraction c(t,T) of the crystalline phase. As shown in a previous paper [10], the data can be fitted well to the Johnsom-Mehl-Avrami (JMA) relation [6,12] …”

“…2. As observed earlier [10], the pure LS 2 glass (c = 0) as well as the fully crystallized ceramic (c = 1) exhibit single straight lines with activation energies E g = (0.69 ± 0.02) eV and E c = (1.30 ± 0.05) eV, respectively. For the two fractions c = 0.05 and c = 0.16, however, in addition to r g dc an additional (metastable) phase becomes observable.…”

“…Generally, the ionic dc conductivity in the crystalline phase, r c dc , turns out to be much lower than the dc conductivity in the glassy phase, r g dc [10]. This is mainly caused by the larger molar volume of the glass, and hence a correspondingly lower activation energy E g than for the crystal (E c ), i.e.…”

“…(3). Hence, the average ionic conductivity of a glass-ceramic depends strongly on the actual fraction c of the crystalline phase, decreasing with rising fraction c from r g dc to r c dc [10]. The experimental findings can be interpreted theoretically using a percolation approach, where the details of the underlying model depend on the microstructure of the actual composite.…”

“…We found that the experimental results for Li-disilicate glass-ceramics can be interpreted best by the general effective media (GEM) approach [11]. The evaluation of the data in terms of this model and of the JMA equation yields basic parameters of the devitrification process such as the activation energy of the crystal growth E d [10].…”