Pure Na-4-mica: Synthesis and Characterization

An innovative synthesis method for phase-pure Na-4-mica has been developed in this study. Phase pure Na-4-mica has been synthesized by using NaCl melt. In the newly developed method, not only could the postpreparation process be avoided but also the crystal size could be manipulated in the range of about 2−5 μm by the initial molar ratio of Al 2 O 3 /NaCl. Both the hydrated and anhydrous Na-4-mica phases possess monoclinic crystal systems with the same layer plane. The X-ray diffraction (XRD) patterns exhibited relatively strong h 0 l peaks along with very strong 00 l peaks. Changes in the cell parameters of β and c on hydration−dehydration indicate that the layer swelling is accompanied with a significant parallel displacement of layers. Furthermore, pure Na-4-mica has exhibited completely reversible dehydration−rehydration behavior up to 800 °C and extremely high Sr 2+ uptake capacity without any layer collapse.