Upconversion phosphors are known as a material system that can convert near-infrared light into visible/ultraviolet emissions by sequentially absorbing multiple photons. The studies on upconversion materials often use...Upconversion phosphors are known as a material system that can convert near-infrared light into visible/ultraviolet emissions by sequentially absorbing multiple photons. The studies on upconversion materials often use two rare earth(RE) ions as a sensitizer-activator pair. We investigated the influences on luminescence intensity depending on Cr-doping content(x) of hexagonal NaLu_(0.98-x)Cr_xF4 Er_(0.02)(x = 0-0.9)upconversion material by substituting Lu^(3+) ions with Cr^(3+)in the absence of Gd^(3+). The change in upconversion luminescence intensity appears with saddle-like shape. We suggest that Cr^(3+) ions play the dual role as a constituent in host lattice and a sensitizer in the upconversion process. Optimal conditions for gaining the strongest upconversion emission correspond to x = 0.3-0.5, where there are effective energy transfers between Cr^(3+) and Er^(3+) ions and Cr-Er dimers. Apart from these values, the emission intensity decreases rapidly which can be ascribed to the absence of multiple-photon absorption for the case of low Cr^(3+) contents, and to the coupling between Cr^(3+) and/or Er^(3+) ions for the case of high Cr^(3+)contents. Magnetization and electron-spin-resonant measurements were performed to understand the correlation between the optical and magnetic properties.展开更多
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2017RIA2B4006388,NRF-2017R1D1A3B03035530)
文摘Upconversion phosphors are known as a material system that can convert near-infrared light into visible/ultraviolet emissions by sequentially absorbing multiple photons. The studies on upconversion materials often use two rare earth(RE) ions as a sensitizer-activator pair. We investigated the influences on luminescence intensity depending on Cr-doping content(x) of hexagonal NaLu_(0.98-x)Cr_xF4 Er_(0.02)(x = 0-0.9)upconversion material by substituting Lu^(3+) ions with Cr^(3+)in the absence of Gd^(3+). The change in upconversion luminescence intensity appears with saddle-like shape. We suggest that Cr^(3+) ions play the dual role as a constituent in host lattice and a sensitizer in the upconversion process. Optimal conditions for gaining the strongest upconversion emission correspond to x = 0.3-0.5, where there are effective energy transfers between Cr^(3+) and Er^(3+) ions and Cr-Er dimers. Apart from these values, the emission intensity decreases rapidly which can be ascribed to the absence of multiple-photon absorption for the case of low Cr^(3+) contents, and to the coupling between Cr^(3+) and/or Er^(3+) ions for the case of high Cr^(3+)contents. Magnetization and electron-spin-resonant measurements were performed to understand the correlation between the optical and magnetic properties.
