Controllable synthesis of metastable γ-Bi₂O₃ architectures and optical properties

Metastable γ-Bi₂O₃ were successfully prepared via a controllable, facile and mild solution precipitation synthesis method in ethylene glycol-water mixed solvent systems without adding surfactant or template agents, at 80 ℃ and ambient atmospheric pressure in 40 min. Ethylene glycol can facilitate the nucleation of γ-Bi₂O₃ as only α-Bi₂O₃ was observed in its absence. And by adjusting ethylene glycol (EG) volume fraction, metastable γ-Bi₂O₃ submicro hexahedrons, tetrahedrons, polyhedrons and three-dimensional self-assembled hierarchical flower-like architectures were obtained respectively. SEM, XRD, and EDS were used to characterize the microstructures. The flower-like metastable γ-Bi₂O₃ architectures with diameter of several micrometers were 3D self-assembled from tetrahedrons step by step. The formation of the hierarchical flower-like architectures was due to the controlling of crystal growth kinetics and the guidance of self-assembly approach by ethylene glycol. The possible formation mechanism of these metastable γ-Bi₂O₃ architectures was also discussed. And compared with α-Bi₂O₃, β-Bi₂O₃, δ-Bi₂O₃, and γ-Bi₂O₃ through other means reported previously, the as-prepared γ-Bi₂O₃ in this paper possesses more excellent optical performance.