Spectroscopic investigation of red Eu3+ doped ceria nanophosphors and promising color rendition for warm white LEDs

Abstract

Europium-ion doped CeO2 phosphors with different Eu3+ concentrations were synthesized via sol-gel combustion synthesis. X-ray diffraction patterns revealed the formation of pure cubic structure of CeO2 even after the incorporation of 35 mol% Eu3+. The excitation spectra of CeO2:Eu3+ displayed a broad band (330–370 nm) and several sharp peaks (393–532 nm) owing to the charge transfer (CT) from O2− to Ce4+ ions and f-f transitions of Eu3+ ions respectively. The evaluation of CT band was explained on the basis of environmental factors. The phosphors were illuminated with blue light and showed the characteristic red luminescence corresponding to the 5D0→ 7FJ transitions of Eu3+ as confirmed from XPS. The emission was observed to increase with the increase in the Eu3+ concentration up to 35 mol% without any quenching. Judd-Ofelt parameters were evaluated using the emission spectroscopy to explain the variation in ligand environment and enhancement of red color purity to 80%. The thermal stability of present phosphors was measured by estimating activation energy and TG-DSC analysis. Robust blue-excitation and sharp red-emission with high color-purity and promising thermal stability in fabricated WLEDs indicated the suitability of CeO2:Eu3+ phosphors for white light emitting diodes with quantum yield efficiency up to 84.6%.