Generation of colour centres in yttria-stabilized zirconia by heavy ion irradiations in theGeV range

Abstract

We have studied the colour centre production in yttria-stabilized zirconia (ZrO2:Y3 + ) by heavy ion irradiation in the GeV range using on-line UV–visibleoptical absorption spectroscopy. Experiments were performed with 11.4 MeV amu − 1 127Xe, 197Au, 208Pb and238U ion irradiations at 8 K or room temperature (RT). A broad and asymmetrical absorptionband peaked at a wavelength about 500 nm is recorded regardless of the irradiationparameters, in agreement with previous RT irradiations with heavy ions in the 100 MeVrange. This band is de-convoluted into two broad Gaussian-shaped bands centred atphoton energies about 2.4 and 3.1 eV that are respectively associated with theF + -type centres (involving a singly ionized oxygen vacancy,VO·) and Tcentres (i.e. Zr3 + in a trigonal symmetry) observed by electron paramagnetic resonance (EPR) spectroscopy. Inthe case of 8 K Au ion irradiation at low fluences, six bands are used at about 1.9, 2.3, 2.7,3.1 and 4.0 eV. The three bands near 2.0–2.5 eV can be assigned to oxygen divacancies (i.e. F2 + centres). No significant effect of the irradiation temperature is found on the widths of allabsorption bands for the same ion and fluence. This is attributed to the inhomogeneousbroadening arising from the static disorder due to the native charge-compensating oxygenvacancies. However, the colour centre production yield is strongly enhanced at 8 K withrespect to RT. When heating irradiated samples from 8 K to RT, the extra colour centresproduced at low temperature do not recover completely to the level of RT irradiation. Thelatter results are accounted for by an electronically driven defect recovery process.