Splitting and broadening of the emission bands of Y_2O _3:Eu~(3+),Nd~(3+) and its dependence on Nd ~(3+) concentration and annealing temperature

摘要

Although Eu~(3+) ion-doped Y_2O_3 has been extensively used as red phosphors, their color rendering needs to be improved for high-quality illumination and displaying. Here, we show that the emission spectra of Y_2O_3:Eu~(3+) red phosphors can be broadened by the doping of Nd~(3+) ion so that the color rendering capability of Y_2O_3:Eu~(3+) was remarkably enhanced. Y_2O_3:Eu~(3+) and Y_2O _3: Eu~(3+),Nd~(3+) colloidal spheres were synthesized by wet chemical procedure and high-temperature treatment. The fluorescence measurement under the 254 and 380 nm ultraviolet excitation indicates that the 612 nm red emission peak of Eu~(3+) can be splitted into two ones by the doping of Nd~(3+) ion, of which the full width at half maximum (FWHM) is broadened from 4.2 nm to 9.6 nm. By varying the concentration of Nd ~(3+) ion, it was determined that the optimal doping concentration of Nd~(3+) ion is of 3 mol% for realizing the strongest emission intensity. The further increase of Nd~(3+) ion exceeding 3 mol% would lead to a concentration quenching phenomenon. The analysis based on XRD spectra and the simplified energy diagram suggested that the doped Nd~(3+) ion not only monitored the growth dynamics, but also took an efficient energy transfer and a cross relaxation process to generate intense emission from Eu~(3+) ion in both of C_2 and S_6 sites, instead of preferable one type of Eu~(3+) site (C_2 or S_6) in the Nd~(3+) undoped sample.