  Highly oxygen defective cerium oxide, e.g. Gd-doped ceria is a sustainable
non-classical electrostrictor with electromechanical properties that are
superior to lead-based piezoelectric metal oxides. Here, we report
electrostriction in co-doped ceria (Sm, Nd) with a nominally low short-range
vacancy-dopant association energy. Such a strategy results in a higher
electrostrictive strain coefficient at lower-frequencies, and unexpected
electromechanical strain saturation and relaxation effects. These outcomes
support the hypothesis that electrostriction is strongly influenced by the
local environment of oxygen vacancy and by the ionic migration blocking factors
built-in the microstructure.
