Host-sensitized luminescence in LaNbO4:Ln3+ (Ln3+ = Eu3+/Tb3+/Dy3+) with different emission colors
In this work, a series of Eu3+, Tb3+, and Dy3+ singly-doped and co-doped LaNbO4 (LNO) phosphors have been synthesized by a high-temperature solid-state reaction route. X-ray diffraction (XRD) along with Rietveld refinement, diffuse reflection spectra, photoluminescence (PL) and cathodoluminescence (CL) properties, decay lifetimes, and PL quantum yields (QYs) were exploited to characterize the phosphors. Under UV excitation, energy transfer process from the host to the activators exists in the singly-doped samples, which leads to tunable emission color from blue to red for LNO:Eu3+, green for LNO:Tb3+, and yellow including white for LNO:Dy3+. In Eu3+ and Tb3+ co-doped phosphors, LNO:Eu3+, Tb3+, the energy transfers from the host to the activators and Tb3+ to Eu3+ ions have also been deduced from the PL spectra, resulting in tunable emission color from green to red by adjusting the concentration ratio of Eu3+ and Tb3+ ions. The decay times monitored at host emission and Tb3+ emission confirm the existence of energy transfer in the as-prepared samples. The best quantum efficiency can reach 43.2% for LNO:0.01Tb3+ among all the as-prepared phosphors. In addition, the CL spectra of LNO:Eu3+/Tb3+/Dy3+ are a little different from their PL spectra because another emission envelope around 530 nm appears in the samples, which is attributed to the bombardment of higher energy excitation source of low-voltage electron beam. However, the characteristic emissions similar to PL spectra were reserved. Moreover, the CL spectrum of LNO:0.02Tb3+ has stronger emission intensity than that of ZnO:Zn commercial product. These results from the PL and CL properties of LNO:Eu3+/Tb3+/Dy3+ suggest their potential in solid-state lighting and display fields.