Enhanced anti-stocks luminescence in LaNbO4:Ln3+ (Ln3+ = Yb3+, Er3+/Ho3+/Tm3+) with abundant color

Abstract

Lanthanide ion doped up-conversion luminescent (UCL) materials, which have the ability to convert near-infrared longer wavelength excitation light into shorter wavelength visible light, have recently drawn much attention. Now, a series of Ln³⁺ (Yb³⁺, Er³⁺/Ho³⁺/Tm³⁺) ions doped LaNbO₄ (LNO) materials were prepared through a two-step route, including a facile sol–gel process and subsequent combustion. In our work, thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), up-conversion luminescence (UCL), energy level diagram, luminescent lifetimes and corresponding CIE were utilized to characterize the properties. A 980 nm laser was employed to excite Yb³⁺ ions to achieve the ²F_7/2 → ²F_5/2 transition, and the LNO:Yb³⁺,Er³⁺/Ho³⁺/Tm³⁺ samples exhibited intense green, yellowish-green and blue emission, respectively. Luminescent spectra at different powers demonstrated the two-photon absorption process; meanwhile, the corresponding energy transfer mechanisms from Yb³⁺ to Ln³⁺ and the emissions of Ln³⁺ under 980 nm laser excitation were described via an energy level diagram. Moreover, multicolor UCL emissions, the optimal intensities and corresponding mechanism were systematically explored via a suite of concentration spectra of different Ln³⁺ ions. At last, the decay lifetimes based on the concentration variation of Yb³⁺ ion demonstrated that the lifetimes are heavily influenced by Yb³⁺ ion.