Dopant size effect on structural and transport properties of nanometric and single-phased TZP

Electrical properties of doped nanocrystalline ceramics of xR2O3–ZrO2 with 1≤x mol% final content≤3.5 of Sc2O3, Yb2O3, Y2O3, Gd2O3 and Sm2O3 were studied. Rare-earth oxide dopants were selected for their lower valence (+3) compared to Zr4+ and for an increase in their ionic radii ranging from 0.087 to 0.109 nm, respectively, from Sc3+ to Sm3+. This systematic study is focused on compositions defined as the minimal dopant concentration at which the tetragonal single-phase is stabilized. These ceramics are characterized by a good purity (quantity of Si less than 0.1 wt.%) and are found to be perfectly stable in temperature, keeping their microstructure constant. Impedance spectroscopy was used to determine the tetragonal zirconia matrix electrical contribution and the internal interface blocking effect. Both specific and blocking conductivities decrease when the dopant ionic radius is increased. The influence of space-charge layers on the increasing blocking effect was suggested.