Synthesis of equal-sized Y2O3:Bi,Eu mono-spheres and their color-tunable photoluminescence and thermal quenching properties

摘要

On the basis of the synthesized equal-sized mono-spheres (similar to 180 nm), the luminescence properties of Y2O3:0.2 mol%Bi,2xmol%Eu (x = 0.1-7) phosphors were investigated in detail. The PL spectra of Y2O3:Bi,Eu mono-spheres displays both the bluish green/blue emission of Bi3+ at 501/410 nm (P-3(1)-S-1(0), Bi3+ in C-2 or S-6 sites) and the red emission of Eu3+ at 612 nm (D-5(0)-F-7(2)) upon 330/375 nm excitation. Increasing the doping concentration of Eu3+ ions in the phosphor mono-spheres significantly enhances Eu3+ emission (D-5(0)-F-7(2)) and reduces-Bi3+ emission (P-3(5)-S-1(0)) due to the effective energy transfer from Bi3+ to Eu3+ ions, At the optimal Eu3+ concentration of 3 mol%, the Y2O3:Bi,Eu mono-spheres show an intense red emission and a high external quantum efficiency of 42.8%. The energy transfer (ET) process from Bi3+ to Eu3+ ions is determined to be a resonant type via dipole-quadrupole interaction with an ET efficiency of 86.3%. By varying the Eu3+ concentration, the luminescence color can be tuned from bluish green to nearly white and eventually to orange red under 330 nm excitation (Bi3+ in C-2 sites), and also can be tuned from blue to pink and then to orange red under 375 nm excitation (Bi3+ in S-6 sites). Temperature-dependent luminescence spectra demonstrated the good thermal stability of the obtained phosphor mono-spheres.