α-Bi_2O_3 microcrystals and microrods: thermal synthesis, structural and luminescence properties

Abstract

α-Bi_2O-3 microcrystals and microrods with pyramidal tips have been grown by a vapour–solid method using pure Bi as starting material. The morphology of the obtained microstructures depends on the annealing temperature and time. At 650 °C and for short annealing times, microcrystals with well defined facets and sizes of tens of microns, as well as clusters of microcrystals, are formed. Microrods were grown at 800 °C, mainly from nucleation sites in the clusters of microcrystals, and reach lengths of hundreds of microns. Micro-Raman spectroscopy measurements reveal the homogeneity of the obtained microstructures regarding the crystalline α-phase. The luminescence properties of the microrods have been investigated by cathodoluminescence in the scanning electron microscope and by photoluminescence in a confocal microscope. The obtained results were correlated with X-ray photoelectron spectroscopy measurements.