Phase evolution and photoluminescence of Eu(3+)-doped ZrO2

Eu3+ doped ZrO2 nanocrystals were prepared by decanoic acid-assisted hydrothermal method. X-ray diffraction, transmission electron microscope, Fourier transform infrared spectroscopy, Ultraviolet-visible diffuse reflection spectroscopy, and photoluminescence spectra were used to characterize the phase evolution, morphology, surface species, and optical properties of the samples. At low Eu3+ content, monoclinic ZrO2 was achieved to show a rod-like morphology. With increasing the Eu3+ content, tetragonal ZrO2 nanocrystals were obtained to show a ball-like shape. Decanoic acid molecules were decorated on the surfaces of ZrO2 nanocrystals, which gave rise to a typical absorption centered at 300 nm. In addition to the characteristic emission of Eu3+, an intense broad emission was detected for pure and Eu(3+)-doped ZrO2 nanocrystals under ultraviolet excitation, which is interpreted in terms of the F/F+ and/or AOD+ centers that are related with the oxygen vacancies.