Experimental Determination of the Crystallization Phase-Boundary Velocity in the Halozeotype CZX‑1

Isothermal crystallization experiments were performed on the halozeotype CZX-1 with 2D temperature- and time-resolved synchrotron X-ray diffraction (TtXRD) and differential scanning calorimetry (DSC). These crystallization experiments demonstrate that the fundamental materials property, the velocity of the phase boundary of the crystallization front, v pb, can be recovered from the Kolmogorov Johnson and Mehl and Avrami (KJMA) model of phase-boundary controlled reactions by introducing the sample volume into the KJMA rate expression. An additional corrective term is required if the sample volume of the crystallization measurement is anisotropic. The concurrent disappearance of the melt and appearance of the crystalline phase demonstrate that no intermediates exist in the crystallization pathway. The velocity of the phase boundary approaches 0 as the glass transition (T g ≈ 30 °C) is approached and at about 10° below melting point (T m = 173 °C). The velocity of the phase boundary reaches a maximum of 30 μm s–1 at 135 °C. Single or near-single crystals are grown under conditions where the v pb is much greater than the rate of nucleation.