Mono-Disperse CaWO4 Microsphere with Hierarchical Structures: Room Temperature Synthesis and its Optical Properties

In this report, an inorganic salt assisted micro-emulsion method was reported for the preparation of mono-disperse CaWO4 microspheres with hierarchical structures. The as-obtained microspheres are composed of tiny nanorods, which have been proved by the field emission scanning electronic microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) observations. The formation of these hierarchical mono-disperse microspheres is considered to be the synergistic effect of both surfactant and the inorganic salt. Based on the time-dependent experiments, a probable formation mechanism based on surface adsorption and oriented attachment has been proposed. The photoluminescence properties of the microspheres were investigated. The generality of this synthetic method for other metal tungstates were also carefully investigated, which indicates that the morphologies of the final product not only depend on the synthetic conditions, but also depend on the growth habit of the materials.