Reentrant phase transformation from crystalline ikaite to amorphous calcium carbonate

Abstract

We report the spontaneous transformation of highly hydrated crystalline ikaite into less hydrated amorphous calcium carbonate (ACC), which has the outer contours of micrometer-sized crystals, a multi-level interconnected porous structure and a very high specific surface area (98.3 cm² g⁻¹). The ikaite was previously obtained by transformation of an uncommon hydrated ACC with as much H₂O as ikaite, synthesized at 2 °C without any additives. The solid-state amorphization was induced by the fast dehydration of the crystal.