Absorption and emission properties of Zr-doped nanoceria synthesised by co-precipitation-hydrothermal treatment route

Abstract

A series of nanoceria samples doped with zirconium (nil to 2 mol%) and a typical sample doped with 1 mol% each of Zr and Eu were synthesised following co-precipitation-hydrothermal treatment route. The main peaks in X-ray diffraction (XRD) patterns of all the samples corresponded to (111), (200), (220) and (311) planes of cubic ceria. The Fourier transform infrared spectra showed bands which were indicative of formation of nanoceria with intercalated/adsorbed water. In Raman spectra, a sharp and intense Raman shift at around 460-462 cm(-1) was observed for all the samples and the peak intensity decreased with increase in mol% doping of Zr. In case of Zr-Eu-doped sample the peak intensity was similar to the undoped ceria. The decrease in intensity could be due to accumulation/precipitation of more numbers of Zr ions on the surface rather than incorporation into ceria lattice. The indirect band gaps estimated from ultraviolet-visible absorption spectra were smaller when compared to the direct ones. The smaller indirect band gaps indicate that Zr-doped nanoparticles with a higher fraction of atoms residing at the surface were available to assist the indirect electron transition from the valence band to the conduction band. Emission spectra obtained by exciting at 300 and 500 nm for all samples are discussed in details. Transmission electron microscope image of a typical sample showed mono-dispersed uniform sized single crystalline doped ceria.