Effect of 130 keV pulsed electron irradiation on the efficiency of radiative transitions in Eu-doped glass-ceramics CaSiO3

Abstract

Polycrystalline glass-ceramic CaSiO 3 doped with Eu 3+ ions was obtained by devitrification. The analysis of the photoluminescent characteristics of the obtained glass-ceramic is carried out. It was found that as a result of the devitrification of CaSiO 3 , two phases are formed, identified as pseudowollastonite (β-CaSiO 3 ) as the dominant phase together with a small percentage of tridymite (SiO 2 ). The UV–Vis optical absorption of Eu 3+ - doped CaSiO 3 was performed using a UV–Vis spectrophotometer. The main objective of this work was to study the effect of the pulsed corpuscular action of electrons accelerated in a field of 130 keV on energy transitions in the Eu 3+ ion. It is found that, upon steady-state excitation of the photoluminescent signal in the PLE spectra of unirradiated samples at wavelengths below 300 nm, two broad excitation peaks are displayed, possibly associated with O − Eu and O − Si CT transitions. Above 300 nm the characteristic excitation band from 7 F 0 ground state to 5 H j , 5 D 4 , 5 G j , 5 L 6 , 5 D 3 , and 5 D 2 states of the Eu 3+ ions are shown. It was found that, as a result of exposure to an electron beam in the photoluminescence spectra of europium, a redistribution of the relative intensities of the 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 transitions occurs. The calculation of the asymmetry ratio of these transitions showed values for an unirradiated sample R 21 = 2.06 and irradiated R 21 = 2.52, which indicates a decrease in the symmetry of the crystal field around Eu 3+ ions after irradiation. Several reasons for the decrease in the relative intensity of the Eu 3+ luminescence signal after electron irradiation, caused by the effect of electrization of the material, intrinsic defects of the matrix, and inhomogeneous phase composition, are discussed. • Eu doped glass-ceramic CaSiO 3 has been produced by the devitrification method. • Absorption band is due to (O-Si) LMCT and SiOHC or NBOHC centers. • Excitation peaks at 227.5 and 244 nm could be associated with O−Eu and O−Si CT transitions, respectively. • There are several possible reasons that promote PL quenching after electron irradiation. • The increase of the R 21 ratio after electron irradiation indicates a luminescent optimization.