Preparation and luminescence of La2O3:Ln3+ (Ln3+ = Eu3+, Tb3+, Dy3+, Sm3+, Er3+, Ho3+, Tm3+, Yb3+/Er3+, Yb3+/Ho3+) microspheres

Multicolor and monodisperse La2O3:Ln3+ (Ln3+ = Eu3+, Tb3+, Dy3+, Sm3+, Er3+, Ho3+, Tm3+, Yb3+/Er3+, Yb3+/Ho3+) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra were employed to characterize the samples. The results indicate that the La2O3 microspheres can be well indexed to the hexagonal La2O3 phase. In addition, the possible formation mechanism and the chemical reaction of each step to form spherical La2O3 microspheres are proposed according to the concerned analysis. The as-obtained particles show strong light emission with different colors corresponding to different Ln3+ ions under ultraviolet-visible light excitation. Under 980 nm NIR irradiation, the Lu2O3:Ln3+ (Ln3+ = Yb3+/Er3+, and Yb3+/Ho3+) microspheres exhibit characteristic up-conversion emissions of red (Er3+, 2H11/2, 4S3/2, 2H11/2 → 4I15/2), and green (Ho3+, 5F4, 5S2, 5F5 → 5I8), respectively. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices.