Effects of Gd3+ and Ga3+ substitution on the local structure and luminescence properties of Y0.97Al3(BO3)4: 0.03Dy3+ single-phase phosphors

Abstract

A series of Y1-x-yAl3–3z(BO3)4: xDy3+, yGd3+ and zGa3+ single-phase phosphors were prepared by solid-phase technique. Subsequently, the samples were analyzed by Rietveld refinement, SEM, FT-IR and XPS to determine their phases, morphologies, and compositions. The results show that Dy3+, Gd3+ and Ga3+ were successfully doped in YAl3(BO3)4 and the prepared phase was very pure without changing the structure of the initial phase. The emission peaks of Y1-xAl3(BO3)4: xDy3+ phosphor at λex= 351 nm are 483 nm and 574 nm, which correspond to 4F9/2 → 6H15/2 and 6H13/2 transitions, respectively. Afterwards, the local crystal field environment of Dy3+ in the luminescence center was improved by replacing Y3+ with Gd3+ and Al3+ with Ga3+, which enhanced the luminescence. At the peak at 574 nm, the doping of Gd3+ increased 1.49 times and that of Ga3+ increased 1.98 times. The internal quantum efficiencies of these two phosphors are as high as 67.23 % and 70.86 %, and the thermal stabilities are 86.7 % and 88.4 %, respectively. We discuss the mechanism of introducing Gd3+ and Ga3+ to produce luminescence enhancement from two aspects. On the one hand, the host activity was analyzed and explained by first-principles calculations combined with diffuse reflectance spectroscopy. On the other hand, dipole moments are introduced to control the local aberration parameters. Finally, 365 nm chip was used to package and test Y0.94Al3(BO3)4: 0.03Dy3+, 0.03Gd3+ and Y0.97Al2.7(BO3)4: 0.03Dy3+, 0.1Ga3+ phosphors. The color rendering indices of the samples was 67.4 and 68.1, respectively, and they emitted bright natural white light. The results indicate that the Y0.94Al3(BO3)4: 0.03Dy3+, 0.03Gd3+ and Y0.97Al2.7(BO3)4: 0.03Dy3+, 0.1Ga3+ single-phase phosphors have potential commercial value as W-led devices.