Colour centre production in yttria-stabilized zirconia by X-ray and electron irradiations: effect of yttria content
Abstract
Yttria-stabilized zirconia (YSZ) single crystals (for 9.5 and 18 mol% yttria)
were irradiated at room temperature (RT) by X-rays (W white spectrum) and
2.5-MeV electrons. The growth curves of the so-called T-centre (for trigonal
centre, i.e. Zr3+ sitting in a trigonal symmetry site) were studied as a function
of absorbed dose, or irradiation time, by UV–visible optical absorption (OA)
spectroscopy and X-band electron paramagnetic resonance spectroscopy. The
defect concentration at saturation and the production rate are increased by a
factor around two for 18 mol% yttria with respect to 9.5 mol%. Defect decay
was then followed after irradiation by OA spectroscopy as a function of
ageing time at RT. Growth and decay curves of the T-centre are modelled on
the basis of rate equations of charge-exchange reactions with the zirconium
lattice ions. Increase in yttrium content is thought to decrease hole trapping
on Zr3+ ions, thereby enhancing T-centre formation.