EXAFS investigation and luminescent properties of nanosized Tb:Lu2O3 phosphors

Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing. The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of about 30 nm. Local structure of Tb ions in Lu2O3 lattice was investigated by an analytical approach based on Fourier transformation of the extended X-ray absorption fine structure (EXAFS) data. X-ray near edge structure (XANES) spectra suggested that all Tb ions doped were tervalence. EXAFS results indicated that Tb ions have entered the Lu2O3 cubic lattice by means of solid solution. The coordination number and first shell Tb-O distance dropped with the increasing of Tb concentration. Emission spectra of the phosphors was shown to be typical for Tb3+ with main components at 542, 550 and 490 nm, derived from irradiative relaxation of 5D4 level. The emission intensity decreased severely with the increasing of Tb concentration from 1 mol.% to 15 mol.%, suggesting a significant concentration quenching above 1 mol.% Tb. The reduction of emission intensity was interpreted by higher distortion derived relaxation among the surface state resident Tb3+ ions.