PAC characterization of Gd and Y doped nanostructured zirconia solid solutions

A perturbed angular correlation (PAC) study as a function of temperature has been carried out on spray pyrolysis-derived powders and compacts of 2.5 mol% Y2O3-ZrO2 and 2 mol% Gd2O3-ZrO2 nanostructured tetragonal zirconias. The powders undergo the ordinary thermal transformation between the two known defective t′- and regular t-tetragonal forms and also a partial and irreversible change to an ordered cubic configuration. The dynamical nature of the t′-form leads to an activation energy of about 0.15 eV for the oxygen vacancies movement. The as-obtained compacts do not exhibit any known cubic nanostructure but some additional contributions. In both of them a hyperfine component assigned to the orthorhombic phase is determined. In the smaller cation Y doped ceramic a small amount of monoclinic phase reflects an incomplete stabilization.