Development and application of novel NMR methodologies for the in situ characterization of crystallization processes of metastable crystalline materials

Abstract

In this contribution we report on the development and application of modern NMR approaches for the in situ characterization of the crystallization of metastable materials. The work was performed within the framework of the DFG priority programme SPP 1415 “Crystalline Non-Equilibrium Phases”. As one of the goals of this project, the development of a NMR methodology which enables an analysis of local structural motifs on short (1–2 Å) and extended (2–6 Å) length scales without the need for fast magic angle spinning (MAS) has been defined, since the enormous centripetal forces which occur during fast sample rotation (up to 107 g) may intervene with the chemical or physical process which is being monitored. To achieve this goal, we developed a magic angle turning probe and pulse sequences allowing to trace the isotropic chemical shifts and heteronuclear dipolar couplings and hence the determination of structural motifs on short and intermediate length scales. With the implementation of novel inductive heating approaches the range of accessible rotation frequencies for in situ high temperature NMR measurements has been enlarged, now covering the νMAS range of 0–10 kHz with an accessible temperature of up to 700°C. Application of NMR methodologies for the characterization of crystallization processes and the structure and dynamics of novel phases, partially in joint collaborations within the priority program, are also reported.