Photoluminescence properties and energy transfer in the color tunable Ba2CaZn2Si6O17:Bi3+, Tb3+, Eu3+ silicate phosphor for white LED applications

摘要

A series of Bi3+, Tb3+, and Eu3+ ions doped (separately, and together) with the Ba2CaZn2Si6O17 (here after called BCZSO) silicate host were prepared by using the solid-state reaction technique. The phase formation and the morphology analysis of this phosphor were investigated by using powder X-ray diffraction (PXRD) patterns, and scanning electron microscope (SEM) images. When excited with 291 nm, the BC(1-x-y)ZSO:xBi(3+), yTb(3+)phosphor revealed a broad blue emission centered at 465 nm (due to Bi3+ ions) accompanied by a few sharp peaks at 487, 545, 585, and 624 nm pertaining to the characteristic transitions of the Tb3+ ions. The BC(1-x-y-z)ZSO:xBi(3+), yTb(3+), zEu(3+) phosphor, when excited at 281 nm, emitted a wide band centered at 465 nm due to the Bi3+ ions, along with a few narrow bands due to other co-dopants. The 545 nm emission band is due to the Tb3+ ions, and the bands at 593, 611, 653, and 704 nm are the characteristic transitions of the Eu3+ ions. The efficiency of the energy transfer from the sensitizer Bi3+ ions to the activator Tb3+ ions was investigated. The critical distance R-c between the Bi3+, and the Tb3+ ions was obtained to be 17.98 angstrom, with respect to the concentration quenching effect. The decay time analysis of the phosphors showed a decreasing trend with increase in the concentration of the activator ions. The CIE chromaticity color coordinates, and the correlated color temperature of these phosphors were calculated. Due to the presence of the Bi3+, and the Tb3+ ions, the color coordinates fall in the bluish white region. Further, the Eu3+ ions when co-doped with the Bi3+/Tb3+ ions, the emission color was shifted towards the near white region. The quantum efficiency of the samples were also measured. The temperature dependent photoluminescence (TDPL) was done for this phosphor, and the corresponding activation energy value of the phosphor was 0.206 eV. These results suggest that the BC(1-x-y-z)ZSO:xBi(3+), yTb(3+), zEu(3+) phosphor can serve as a good candidate in white light emitting diodes (WLEDs) applications.