Abstract
The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La3+ into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La3+ into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La3+ is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La3+ occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La3+ occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere.
Highlights
The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied
Since Kroger concluded that the lattice group (WO422/WO662) itself was responsible for the luminescence origin[4], what influenced tungstates luminescence properties was explored extensively such as morphology, size and dimension[5,6]
The crystal structure of pure Y2WO6 is monoclinic phase with space group 13-P12/C1-C2h4 reported by Efremov[41], whose inorganic crystal structure database (ICSD) number is 20955
Summary
Bangfu Ding[1], Chao Han[1], Lirong Zheng[2], Junying Zhang[1], Rongming Wang3 & Zilong Tang[4]. The impurity can be any elements for the non-isovalent doping, such as trivalent rare earth and monovalent alkaline metal ions[17,18] This method has been extensively investigated in luminescent compounds, photocatalysts, and magnetic materials. La31-doped ZnO has high photocatalytic activity[19], and LaCoMnO6 presents the coexistence of ferromagnetic and antiferromagnetic properties with increased Ca21 substitution amounts[20] This approach mainly aims at enhancing luminescent intensity, changing optical activity, or broadening emission wavelength range[21,22,23]. We[40] found that the atmosphere and calcination temperature induced the changes of oxygen vacancy concentration and tungsten coordination number in monoclinic Y2WO6, and affected the appearance of longwave excitation and near-infrared emission bands. The change of oxygen vacancy energy states generates different luminescence phenomenon
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