RESUMEN
A remarkable increase in the luminescent intensity of Er3+-doped CaF2 up-conversion phosphors was achieved, showing an approximate enhancement of over 1100-fold. This enhancement was realized by incorporating Yb3+, Al3+, Sr2+, and gold nanospheres and nanorods. The substantial improvement in up-converting luminescence effectively enhances sensitivity and efficiency at low excitation power densities. The up-conversion phosphors, consisting of (Ca,Sr)F2:Er,Yb,Al, were easily prepared using excess NH4F flux at 950 °C for 30 min. The structural confirmation of interstitial Al3+ ions within the CaF2 lattice was achieved through synchrotron powder X-ray powder diffraction. The significant enhancement of up-conversion emission and their mechanisms in the phosphors were vividly represented through energy transfer, interstitials and local distortions, and localized surface plasmon resonances when excited with a 980 nm diode laser.
RESUMEN
Garnet-type materials consisting of Y3Al5-2x(Mg,Ge)xO12 (x = 0, 1, 2), combined with Eu3+ or Ce3+ activator ions, were prepared by a solid-state method to determine the structural and optical correlations. The structure of Y3Al5-2x(Mg,Ge)xO12 (x = 1, 2) was determined to be a cubic unit cell (Ia-3d), which contains an 8-coordinated Y3+ site with octahedral (Mg,Al)O6 and tetrahedral (Al,Ge)O4 polyhedra, using synchrotron powder X-ray diffraction. When Eu3+ or Ce3+ ions were substituted for the Y3+ site in the Y3Al5-2x(Mg,Ge)xO12 host lattices, the emission spectra showed a decrease in the magnetic dipole f-f Eu3+ transition and a redshift of the d-f Ce3+ transition, related to centrosymmetry and crystal field splitting, respectively. These changes were monitored according to the increase in Mg2+ and Ge4+ contents. The dodecahedral and octahedral edge sharing was identified as a key distortion factor for the structure-correlated luminescence in the Eu3+/Ce3+-doped Y3Al5-2x(Mg,Ge)xO12 garnet phosphors.