Effects of Al3+ substitution on the luminescence properties of LuNbO4 doped with Eu3+ and Tb3+ ions

摘要： The effect of Al3+ substitution on the enhancement of the luminescence of Lu1–xAlxNbO4:Eu3+ and Lu1–xAlxNbO4:Tb3+ was investigated. X-ray diffraction patterns confirmed that the Eu3+, Tb3+, and Al3+ ions were fully incorporated into the Lu3+ sites. In the case of Lu1–xAlxNbO4:Eu3+, the predominant red emission (614 nm) was assigned to the 5D0 → 7F2 transition of Eu3+ and for x = 0–0.05, its intensity increased up to ~125 and 108% under 395 nm (7F0 → 5L6) and a charge transfer band excitation, respectively. For Lu1–xAlxNbO4:Tb3+, the strongest emission band peaking at 551 nm was attained in the green region among multiple emission bands corresponding to the 5D4 → 7FJ transitions of Tb3+. Increasing the x values from 0 to 0.05 increased the green emission significantly by ~137%. These phenomena were explained by the local structural distortions and crystal field asymmetry surrounding Eu3+ and Tb3+, which were attributed to a large difference in the ionic radii of Al3+ and Lu3+.