Threshold displacement energy in yttria-stabilized zirconia

We have studied the color center production in yttria-stabilized zirconia single crystals (i.e. ZrO2: Y with 9.5 mol% Y2O3) with the (100) orientation, by electron irradiations at energies ranging between 1.0 and 2.5 MeV. Electron paramagnetic resonance (EPR) measurements show that three paramagnetic centers are stable at room-temperature: i) an F+-type center (singly ionized oxygen vacancy), ii) the so-called T-center (Zr3+ in a trigonal oxygen environment), and iii) a hole center. The growth curves of F+-type centers at variable electron energy cannot be rescaled versus the absorbed dose. These data confirm that F+-type center production is primarily governed by elastic collision processes with a threshold electron energy about 1.0 MeV. This can be correlated to a threshold displacement energy either about 120 eV for the O-atoms in the collision cascades, or about 80 eV for the Zr- (or Y-) atoms. In contrast, the growth curves of T-centers at variable electron energy are rescaled versus the absorbed dose. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)