Oxygen defective cerium oxides CeO2-δ exhibits a non-classical giant electromechanical response that is superior to lead-based electrostrictors. In this work, we report the key-role of acceptor dopants, with different size and valence (Mg2+, Sc3+, Gd3+, and La3+), on polycrystalline bulk ceria. Different dopants tune the electrostrictive properties by changing the electrosteric dopant-defect interactions. We find two distinct electromechanical behaviors: when the interaction is weak (dopant-vacancy binding energy ≤ 0.3 eV), electrostriction displays high coefficient (M_33), up to 10−17 (m/V)2, with strongly time-dependent effects. In contrast, we observe no time-dependent effects when the interaction becomes strong (≥ 0.6 eV).