Publication Date:
2015-02-10
Description:
The crystallization of hexagonal NdCO 3 OH through hydrothermal synthesis carried out at slow (reaching the desired temperature within 100 min) and quick (50 min) rates of heating but at variable temperatures (165–220°C) are reported here. The formation of NdCO 3 OH occurs via the crystallization of an amorphous precursor. Both the precursor and the crystalline NdCO 3 OH were characterized by X-ray diffraction, infrared spectroscopy and high-resolution electron microscopy. The mechanism of crystallization is very dependent on the experimental conditions (rate of heating and temperature treatment). With increasing temperature, the habit of NdCO 3 OH crystals changes progressively to more complex spherulitic or dendritic morphologies. The development of these crystal morphologies is suggested here to be controlled by the level at which supersaturation was reached in the aqueous solution during the breakdown of the amorphous precursor. At the highest temperature (220°C) and during rapid heating (50 min) the amorphous precursor breaks down rapidly and the fast supersaturation promotes spherulitic growth. At the lowest temperature (165°C) and slow heating (100 min), however, the supersaturation levels are approached more slowly than required for spherulitic growth, and thus more regular, previously unseen, triangular pyramidal shapes form.
Print ISSN:
0026-461X
Electronic ISSN:
1471-8022
Topics:
Geosciences
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