Avrami equation

An equation, describing crystallization kinetics, of the form:

$1 − φ c = e − K t n$

where $φ c$ is the crystalline volume fraction developed at time $t$ and constant temperature, $K$ and $n$ are suitable parameters. $K$ is temperature dependent. According to the original theory, $n$ should be an integer from 1 to 4, the value of which should depend only on the type of the statistical model; however, it has become customary to regard it as an adjustable parameter that may be non-integral.

Source:

Purple Book, p. 85