Hong Chae Jung

Excitation induced efficient luminescent properties of nanocrystalline Tb3+/Sm3+:Ca2Gd8Si6O26 phosphors

The cathodoluminescence and the excitation induced photoluminescence properties have been investigated for the nanocrystalline Tb3+/Sm3+:Ca2Gd8Si6O26 phosphors prepared by a solvothermal reaction method. The XRD patterns confirm their hexagonal structure. The green, orange and white emissions have been obtained by exciting at 275, 378, and 405 nm wavelengths, respectively. The corresponding CIE chromaticity coordinates are found to be in close proximity to the standard points in their respective regions. The cathodoluminescence at low accelerating voltage has also covered the entire visible region, resulting in white emission. These luminescent powders are expected to find potential applications in the development of LEDs and FEDs.

Gd3 + Sensitization Effect on the Luminescence Properties of Tb3 + Activated Calcium Gadolinium Oxyapatite Nanophosphors

The solvothermal synthesis and structural characterization of silicate based oxyapatite Tb 3+ activated Ca 2 Gd 8 Si 6 O 26 (CGS) nanophosphors have been reported. The structure of these phosphors was elucidated by the powder x-ray diffraction (XRD) and further characterized by scanning electron microscopy. The XRD results revealed that the obtained Tb 3+ :CGS shows the characteristic peaks of oxyapatite in a hexagonal lattice structure. The photoluminescence (PL) properties were studied with variations of Tb 3+ concentration and sintering temperature. Under 275 nm excitation, both Tb 3+ ( 5 D 3,4 → 7 F J=6.5.4.3 ) and Gd 3+ ( 6 P 7/2 → 8 S 7/2 ) characteristic emissions associated with 4f-4f transitions have been observed, and when the concentration of Tb 3+ increases above 1 mol % the 5 D 3 emission intensity decreases due to cross relaxation. The Gd 3+ emission intensity decreases with increasing Tb 3+ concentration and the PL intensity of Tb 3+ at 378 nm excitation was much weaker than the obtained intensity with excitation at 275 nm, suggesting that the efficient energy transfer occurred from Gd 3+ to Tb 3+ ions in CGS host lattice. The decay curves of the 5 D 4 level show that the lifetime decreases with increasing crystallite size and concentration of Tb 3+ ions. These luminescent powders are expected to find potential applications such as white light emitting diodes and optical display systems.