Photoluminescent properties of new up-conversion phosphors of Yb/Tm co-doped (Gd_(1-x)Lu_x)_3Al_5O_(12) (x = 0.1-0.5) garnet solid solutions

摘要

The metastable garnet lattice of gadolinium aluminate garnet (Gd_3Al_5O_(12). GdAG) has been effectively stabilized by doping with significantly smaller Lu~(3+), which then allows a facile incorporation of rare earth activators for opto-functionality explorations. Carbonate precursors of Yb/Tm codoped (Gd_(1-x)Lu_x)_3Al_5O_(12). with an approximate composition of (NH_4)_xLn_3Al_5(OH)_y(CO_3)_z - nH_2O (Ln = Gd, Lu, Yb and Tm), were coprecipitated from the mixed solution of ammonium aluminum sulfate and rare earth nitrates, using ammonium hydrogen carbonate as the precipitant. The resultant [(Gd_(1-x)Lu_x)_(0.948)Yb_(0.05)Tm_(0.002)]_3Al_5O_(12) (x = 0.1-0.5) garnet solid-solution particles, with good dispersion and fairly uniform particle morphologies, exhibit a strong blue emission centered at ~487 nm (the ~1G_4->~3H_6 transition of Tm~(3+)) and a weak red emission centered at ~650 nm (the ~1G_4->~3F_4 transition of Tm~(3+)) under laser excitation at 978 nm. Meanwhile, the dependence of up-conversion emission intensity on the pumping power was discussed. Partially replacing Gd~(3+) with Lu~(3+) up to 50 at.% (x = 0.5) does not appreciably alter peak positions of the up-conversion emission bands but tends to yield decreased lattice parameters of the material and lowered emission intensities. The Yb/Tm codoped (Gd.Lu)AG garnet system developed herein may potentially be used as a new type of optical material.