EPR g-tensor of paramagnetic centers in yttria-stabilized zirconia from first-principles calculations

In order to assign the defect responsible for the experimental electron paramagnetic resonance (EPR) signal with trigonal symmetry (T center), we have studied the properties of different paramagnetic centers in yttria-stabilized cubic zirconia by computing the EPR g-tensor from density functional perturbation theory. We have considered reduced vacancy-zirconium complexes and reduced Ti impurities. These first-principles calculations allow us to discard the experimental assignment of the T center to an extrinsic Ti3+ ion nearest neighbor to a single vacancy. Instead, the calculated EPR g tensors of both a Zr3+ or a Ti3+ ion at the center of a divacancy aligned along the < 111 > directions are compatible with the experimental EPR signal. However, since the EPR signal of the T center is correlated experimentally with an optical absorption band at 370 nm, calculated optical excitations allow us to decide in favor of the Ti3+ divacancy complex.