Photoluminescence study of (Sm0.95 Ce0.05)2O3 nanoparticles for LED applications

Abstract

Nanophosphors are a blazing area which has gained momentum in the present day research due to the fabulous unique properties of nanoparticles from their respective bulk. The rare earth doped sesquioxides have received considerable attention due to its unique properties like high chemical and thermal stabilities, intense UV absorption and also its use in solid state lightings, LASERS and so on. Here, we have synthesized (Sm0.95 Ce0.05)2O3 nanocrystalline powder using combustion method. Powder X-ray diffraction was used to study the structural characterization of the synthesized sample and the result confirmed that the synthesized nanoparticles had a nanocrystalline structure with a cubic phase and Ia3¯ space group. The crystal structure and the shape of the particles have a tremendous effect on the photoluminescent properties. The surface morphology and the size of the particles were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM micrographs showed that t he synthesized particles appear to be spherical. The TEM results confirmed that the particles formed were spherical and in nano regime. Phosphors with spherical morphology will surely enhance the photoluminescent properties of the materials. Hence the synthesized sample will have good luminescent characteristics. The optical properties of the sample were studied using ultraviolet –visible (UV-Vis) data analysis and photoluminescence (PL) studies. The absorption peaks obtained are at 364nm, 376, 405, 464 nm and 476nm which correspond to 6H5/2 → 4D3/2, 6H5/2 → 4D1/2, 6H5/2 → 6F7/2, 6H5/2 → 4I13/2 and 6H5/2 → 4I11/2 transitions respectively. On excitation, these particles showed a strong emission at 605 nm which corresponds to 4G5/2 → 6H7/2 transition and other emissions at 563 nm and 647nm correspond to 4G5/2 → 6H5/2 and 4G5/2 → 6H5/2 transitions revealing that it is an orange-red emissive phosphor. This novel nanophosphor can offer new possibilities for the development of white light-emitting diodes (WLEDs) which can be excited by the near-UV chips and also in solid state lightings.