Tunable luminescence and energy transfer in Tb3+,Eu3+ co-doped Gd2Zr2O7 phosphors with high thermal stability for WLEDs

Red phosphors with good thermal stability, high color temperature and color purity are critical in high power warm white LED devices. Herein, a series of single and co-doped Tb 3+ ,Eu 3+ polychromatic phosphors with pyrochlore structure based on Gd 2 Zr 2 O 7 have been prepared for the first time by a conventional solid phase reaction method. Compared to single doped Eu 3+ phosphors, Tb 3+ ,Eu 3+ co-doped phosphors possess following advantages: improved UV absorption, increased photoluminescence intensity, extended luminescence range and improved thermal stability. At room temperature, the Gd 2 Zr 2 O 7 :Tb 3+ ,Eu 3+ phosphors exhibited a gradual shift from yellow-green emission at 544 nm to orange-red emission at 613 nm with increasing doping of Eu 3+ ions. Energy transfer efficiency has been evaluated to be 71% by analyzing the fluorescence lifetime of Tb 3+ ions. The concentration quenching mechanism under different conditions was analyzed in detail and it was concluded that the quenching of Tb 3+ is caused by dipole-dipole interaction. In addition, the activation energy (ΔE a ) of the Gd 1.92 Zr 2 O 7 :0.03Tb 3+ ,0.05Eu 3+ phosphor was calculated to be as high as 0.2674 eV compared to other Tb 3+ , Eu 3+ co-doped phosphors, demonstrating its high thermal stability. WLEDs devices based on Gd 1.92 Zr 2 O 7 :0.03Tb 3+ ,0.05Eu 3+ phosphors have been prepared, which have low correlated color temperature (CCT) (5283 K), high color rendering index Ra = 85.5 K) and CIE coordinates chromaticity coordinate (0.3371,0.3333). All of the results show that Gd 2 Zr 2 O 7 :Tb 3+ ,Eu 3+ phosphors provide a new avenue to develop high quality red emission and high thermal stability phosphors for WLEDs.