Fast crystallization below the glass transition temperature in hyperquenched systems

The Journal of Chemical Physics, vol. 158, pp. 054502

Abstract

Many phase change materials (PCMs) are found to crystallize without exhibiting a glass transition endotherm upon reheating. In this paper, we review experimental evidence revealing that these PCMs and likely other hyperquenched molecular and metallic systems can crystallize from the glassy state when reheated at a standard rate. Among these evidences, PCMs annealed below the glass transition temperature Tg exhibit slower crystallization kinetics despite an increase in the number of sub-critical nuclei that should promote the crystallization speed. Flash calorimetry uncovers the glass transition endotherm hidden by crystallization and reveals a distinct change in kinetics when crystallization switches from the glassy to the supercooled liquid state. The resulting Tg value also rationalizes the presence of the pre-Tg relaxation exotherm ubiquitous of hyperquenched systems. Finally, the shift in crystallization temperature during annealing exhibits a non-exponential decay that is characteristic of structural relaxation in the glass. Modeling using a modified Turnbull equation for nucleation rate supports the existence of sub-Tg fast crystallization and emphasizes the benefit of a fragile-to-strong transition for PCM applications due to a reduction in crystallization at low temperature (improved data retention) and increasing its speed at high temperature (faster computing).

Authors 5

1. Pierre Lucas

   University of Arizona

   Affiliation as printed

   Department of Materials Science and Engineering, University of Arizona 1 , Tucson, Arizona 85712, USA

2. Wataru Takeda

   University of Arizona

   Affiliation as printed

   Department of Materials Science and Engineering, University of Arizona 1 , Tucson, Arizona 85712, USA

3. Julian Pries Aachen Institute of Physics IA

   RWTH Aachen University

   Affiliation as printed

   Institute of Physics IA, RWTH Aachen University 2 , 52074 Aachen, Germany

4. Julia Benke‐Jacob Aachen Institute of Physics IA

   RWTH Aachen University

   Affiliation as printed

   Institute of Physics IA, RWTH Aachen University 2 , 52074 Aachen, Germany

5. Matthias Wuttig Aachen Institute of Physics IA

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Institute of Physics IA, RWTH Aachen University 2 , 52074 Aachen, Germany

   Peter Grünberg Institute (PGI 10) 3 , Forschungszentrum Jülich, 52428 Jülich, Germany