Physical Processes - Isoconversional Kinetics of Thermally Stimulated Processes - page 121

Fig. 3.49 Arrhenius plot
for the kinetics of the phase
transition between the ʲ and
ʳ forms of Li 2 ZnSiO 4 . T c is
the equilibrium transition
temperature. (Reproduced
from Villafuerte-Castrejon
and West [ 142 ] with permis-
sion of RSC)

predict the temperature dependence of the effective activation energy. The equation
that can be used for this purpose is Eq. 3.45. Variation of temperature around T 0
produces the E versus T dependence displayed in Fig. 3.50 . It is seen that the depen-
dence has a discontinuity at T 0 . On heating above T 0 , the activation energy for the
transition from the phase II to I decreases from + ∞ down to the activation energy of
diffusion E D . On cooling below T 0 , the activation energy for the transition from the
phase I to II increases from − ∞ toward 0. If the phase I can be supercooled below
T max , its heating would result in the transition from the phase I to II. For this process,
the activation energy would decrease from E D toward 0.

Fig. 3.50 Theoretical E
versus T dependence derived
from Eq. 3.45

phase II phase I

supercooled
phase I

E=E D

E=0

T