Europium luminescence as a structural probe to understand defect evolution in CeO2/Eu3+, M3+ (M = Y and La): contrasting role of codopant ionic size.

Defect engineering to tune the light emission properties has been fetching lot of interest among scientific community for designing efficient optoelectronics and light-emitting diodes. Defect evolution in the trivalent ion-doped CeO2 and their dependence on the ionic radii of the trivalent dopant were probed using Rietveld refined powder X-ray diffraction, positron annihilation lifetime and photoluminescence spectroscopy. The photoluminescence of Eu3+, a known structural probe, is monitored with codoping of two other trivalent ions Y3+ and La3+ whose ionic radii are on either side of Eu3+. The studies showed that smaller dopants like Y3+ create oxygen vacancies that are closely associated with Y3+ and codoping does not cause significant enhancement in asymmetry in the emission from Eu3+. At the same time, vacancies created by La3+ are not strongly associated with La3+, and due to their stronger association with Eu3+, the asymmetry in the emission is enhanced. The study shows the usefulness of emission from Eu3+ as probe in understanding the effect of different trivalent dopants using them as codopants to Eu3+. The studies are expected to help in tuning the oxygen vacancy concentration as well as their migration in CeO2 for technological applications such as catalysis, magnetism and conductors. This work highlighted role of defect engineering in tailoring the optical properties of red emitting CeO2:Eu3+ phosphor via aliovalent and contrasting Y3+ and La3+ co-dopant. [ABSTRACT FROM AUTHOR]