Construction of EuF3 hollow sub-microspheres and single-crystal hexagonal microdiscs via Ostwald ripening and oriented attachment

Abstract

Hexagonal phase EuF3 hollow sub-microspheres and single-crystal hexagonal microdiscs with controllable sizes were fabricated via a facile hydrothermal route at 110 °C for 8 and 14 h, respectively. Increasing the Eu(NO3)3 concentration (from 0.125 to 0.2 M) increased the size of the microdiscs, but decreased the diameter of the sub-microspheres. Detailed investigations on samples at different preparation stages revealed that the hollow sub-microspheres were formed via a self-transformation process within the same aggregated particles accompanied by the localized Ostwald ripening. Subsequently, hexagonal microdiscs were achieved at the consumption of the hollow sub-microspheres, which were attributed to oriented attachment mechanism. Moreover, the Ostwald ripening mechanism acted to form the secondary particles before the attachment. This kind of cooperation of two basic mechanisms may give us a new insight into the growth of EuF3 microcrystals and opens a new way for controllable synthesis of other well-defined crystals in morphology and dimensionality.