LUMINESCENCE OF POLYCRYSTALLINE CUBIC AND TETRAGONAL YTTRIA-STABILIZED ZIRCONIA

Polycrystalline cubic and tetragonal yttria-stabilized zirconia samples were investigated by means of photoluminescence (PL) experiments. Emission and excitation spectra are reported in the 90-300 K temperature range. For all the samples the emission spectra show substantially the same shape with a dominant peak at about 2.1 eV (590 nm) in good agreement with previous studies. In contrast, the excitation spectra of the 2.1 eV emission exhibit a shape which depends on the kind of sample and peaks in the 4.68 eV (265 nm) to 4.51 eV (275 nm) range. From temperature dependence measurements the activation energy of the thermal quenching was found to lie between 0.12 and 0.10 eV. Significant differences in the shape of the time-resolved spectra of cubic and tetragonal polycrystals were seen. Luminescent decays were satisfactorily fitted by two exponential functions and the temperature dependence of the total life times was found to be consistent with a mixed-state model. The results are discussed on the basis of colour centres and the presence of grain boundaries and other quenching defects generated in the samples.