Tracking Amorphous Calcium Carbonate Crystallization Products with Far-Infrared Spectroscopy

We prepared solution-precipitated amorphous calcium carbonate by two similar methods and tracked structural changes over time as they crystallized. By cross-referencing mid-range infrared (400-4000 cm(-1)) with far-infrared (100-400 cm(-1)) spectral features, and by comparing with powder X-ray diffraction data for the aged crystallized products, we provide guidelines for-and potential limitations of-using far-infrared spectroscopy to assess multi-phase Mg-containing calcium carbonate samples that include amorphous or poorly crystallized components.