Optical properties of nanocrystal and bulk ZrO2: Eu3+

Optical properties of Eu3+ ions were studied in nanocrystal and bulk zirconia. Under 394 nm excitation, the emission spectra show the stronger emission at 614 nm, whose emission with respect to the magnetic dipole transition in the bulk is stronger than that in the nanocrystallite. According to the absorption spectra and 614 nm emission-excitation spectra, the charge-transfer (CT) state energy of the bulk is higher than that of the crystallite. The relative 614 nm-emission intensity is proportional to the CT state energy whether in the bulk or in the crystallite. Additionally, the fourier infrared transfer (FIT) spectra show that a few Cl atoms exist in the two samples. The CT states of the two samples are considered to originate from the superposition of O2− to Eu3+ CT state and Cl− to Eu3+ CT state.