Figure 6.

(a) Plot showing a decline of activation area for crack growth versus CTE of the glass, indicating indirectly that the parameter A* decreases with increasing reactivity of the glass caused by higher alkali and alkaline earth oxide contents. (b) Dependence of the activation area with $G$, according to the data shown in Fig. 2. The lines are theoretical boundaries ( $A\ast =\text{mkT}/2G$) taking m from the fittings summarized in Table 2.