Controlled Synthesis and Microstructure of Metastable Flower-Like Vaterite.

Developing a simple morphology-controlled synthesis of metastable vaterite is a goal in the field of materials research. In this paper, we successfully synthesized flower-like dendritic vaterite crystals using a microwave method with 2-naphthaleneacetic acid (2-NAA) and ethylene glycol (EG) as the regulating additives. The results show that the morphology of vaterite could be regulated by inducing a monolayer or multilayer flower-like structure with the appropriate choice of regulators. Interestingly, the microstructure analysis showed that such flower-like vaterite dendrites host two different kinds of crystal cells. The negative carbonate 2-NAA effectively neutralized the charge of the vaterite (001) plane, resulting in the crystalline growth along the direction parallel to it and inducing a flower-like morphology. This experiment reveals an alternative approach to controlling hierarchical structures during the synthesis of similar classes of minerals.