Luminescence properties of red-emitting Ca2Al2SiO7:Eu3+ nanoparticles prepared by sol-gel method

A series of red-emitting Ca2−xAl2SiO7:xEu3+ (x = 1 mol.%–10 mol.%) phosphors were synthesized by the sol-gel method. The effects of annealing temperature and doping concentration on the crystal structure and luminescence properties of Ca2Al2SiO7:Eu3+ phosphors were investigated. X-ray diffraction (XRD) profiles showed that all peaks could be attributed to the tetragonal Ca2Al2SiO7 phase when the sample was annealed at 1000°C. Scanning electron microscopy (SEM) micrographs indicate that the phosphors have an irregularly rounded morphology with particles of about 200 nm. Excitation spectra showed that the strong broad band at around 258 nm and weak sharp lines in 350–490 nm were attributed to the charge transfer band of Eu3+-O2− and f-f transitions within the 4f6 configuration of Eu3+ ions, respectively. Emission spectra implied that the red luminescence could be attributed to the transitions from the 5D0 excited level to the 7FJ (J = 0, 1, 2, 3, 4) levels of Eu3+ ions with the main electric dipole transition 5D0→7F2 (618 and 620 nm), and Eu3+ ions prefer to occupy a lower symmetry site in the crystal lattice. Moreover, the photoluminescence (PL) intensity was strongly dependent on both the sintering temperature and doping concentration, and the highest PL intensity was observed at an Eu3+ concentration x = 7 mol.% after annealing at 1100°C. The obtained Ca2Al2SiO7:Eu3+ phosphor may have potential application for the red lamp phosphor.