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

Abstract

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⁺, ²H_11/2, ⁴S_3/2, ²H_11/2 → ⁴I_15/2), 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.