Relationship between optical properties and crystallinity of nanometer Y2O3:Eu phosphor

Abstract

${\mathrm{Y}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ -doped ${\mathrm{Eu}}^{\mathrm{3+}}\mathrm{\hspace{0.17em}(}{\mathrm{Y}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{:Eu})$ nanometer particles (NPs) were synthesized via a chemical route. The particle size estimated by x-ray diffractometry and transmission electron microscopy was about 61 nm. Two photoluminescence peaks were observed at 582 and 587 nm, being attributed to the transition of ${}^5{D}_0{\to }^7{F}_{\text{1a}}$ of ${\mathrm{Eu}}^{\mathrm{3+}}$ in the $S_6$ and $C_2$ symmetry sites of ${\mathrm{Y}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}},$ respectively. The intensity ratio of the photoluminescence peaks at 582 nm to at 587 nm was larger for NPs than for micrometer particles (MPs). The excitation peak of NPs due to the charge-transfer band shifted toward the high-energy side as compared with that of MPs. According to x-ray diffractometry, the lattice distortion and the lattice constant were larger for NPs than for MPs, showing the restructure at the near surface and the increase in ionicity of the Eu–O bond with decreasing particle size. This explains the blueshift in the excitation peak.