Ultraviolet and blue cathodoluminescence from cubic Y2O3 and Y2O3:Eu3+ generated in a transmission electron microscope

Herein we describe the investigation of cubic spherical submicron particles of non-doped Y2O3 and Y2O3 doped with Eu 3+ in a transmission electron microscope (TEM) equipped with a spectrometer to detect cathodoluminescence from individual particles. Each submicron particle was made up of nanometre sized crystals. We found that these crystals showed a broad emission band at 353 nm upon bombardment with 200 keV or 80 keV electrons. Upon increasing the Eu concentration from 0 to 2 mol% this UV/blue emission was gradually quenched: at Eu concentrations 42 mol% no UV/blue emission was detected, only the well-known cathodoluminescence (CL) spectrum of Y2O3:Eu 3+ could be recorded. This UV/blue emission has been attributed to the intrinsic luminescence of Y2O3 caused by self-trapped excitons. We found that the UV/blue luminescence was strongly temperature dependent and that the trap depth of the self-trapped excitons was 0.14 eV. The ratios of the spectral radiances of D1 FJ and D0 FJ (J = 0, 1. . .6) Eu 3+ transitions in the CL-TEM spectra of Y2O3:Eu 3+ at low Eu concentrations was about a factor of 10 larger than those recorded at 15 keV. This phenomenon has been explained by absorption of the intrinsic luminescence of Y2O3 by Eu .