THE SYNTHESIS, CHARACTERIZATION, AND UPCONVERTING PROPERTIES OF ERBIUM DOPED; YTTERBIUM, ERBIUM CO-DOPED YTTRIUM OXYSULFIDE PHOSPHORS UNDER 808, 980, AND 1560 nm EXCITATION

Bulk yttrium oxysulfide phosphors were prepared using the polysulfide flux method. The morphology and structure was characterized using transmission electron microscopy and x-ray powdered diffraction. Visible emissions occurring near 530 and 550 nm and 660 670 nm consistent with the H11/2, S3/2 → I15/2 and F9/2 → I15/2 transitions, respectively, were observed under 808, 980, and 1560 nm excitation. The upconverting mechanisms excited at 808, 980, and 1560 nm have been investigated in detail. The power dependent behavior of the upconverted emission intensities for singly doped erbium phosphors excited at 808 and 980 nm indicated a two-photon excitation process. Likewise, the ytterbium and erbium co-doped phosphors excited at 980 nm also indicated a two-photon excitation process. Doping with 10% erbium showed the most intense emissions under 808 and 1560 nm excitation. Yttrium oxysulfide co-doped with 15% ytterbium and 3% erbium showed the most intense emissions under 980 nm excitation. Upon 1560 nm excitation, the intensity of the red emission band was significantly enhanced by co-doping erbium with ytterbium. Concentration quenching became apparent when either the concentration of erbium or ytterbium reached 20%.