On the abnormal efficiency of the luminescence of submicron-sized phosphor Y$_2$O$_3$ : Eu$^{3+}$

Samples of the Y$_2$O$_3$ : Eu$^{3+}$ (5–11 at%) phosphor with a high luminescence efficiency have been synthesized by the sol-gel method. The chemical, substructural, and optical properties of the material have been investigated using the thermal analysis, X-ray powder diffraction, electron microscopy, vibrational and Raman spectroscopy, and diffuse reflection methods. The size effect of particles and crystallites on the luminescence parameters of the phosphor has been analyzed. It has been found that the submicron-sized Y$_2$O$_3$ : Eu$^{3+}$ phosphor containing 9–11 at% Eu$^{3+}$ exhibits an abnormally high luminescence intensity. It has been shown that these effects are associated with the enrichment of the surface of particles and crystallites with dopant ions due to the decrease in the local symmetry of their environment.