Revealing the Giant Electromechanical Effects in Yttria-Stabilized Zirconia Single Crystal

Ionic conductors exhibiting giant electromechanical responses have emerged as promising alternatives to lead-based relaxor ferroelectrics for high-resolution actuators and sensors. However, the role of long-range oxygen-vacancy migration in governing electromechanical properties remains unclear and even controversial. Yttria-stabilized zirconia single crystal (SC-YSZ) provides an ideal model system to elucidate the origin of electrostriction and piezoelectricity with oxygen-vacancy migration, owing to the absence of grain boundaries and substrate constraints. Here, atomic force microscopy (AFM) is employed to probe the electromechanical coupling responses of SC-YSZ, displaying pronounced orientation-dependent features and non-intrinsicity in [100]-, [110]-, and [111]-oriented SC-YSZs. Notably, the giant electrostrictive coefficient |M₃₃| of 5.82 × 10^-17 m² V^-2 and remarkable pseudo-piezoelectric coefficient |d₃₃| of 218 pm V^-1 are obtained at the frequency of 10 mHz in [100]-oriented SC-YSZ. Local relaxation measurements, macroscopic ionic conductivity, and first-principles calculations reveal that the orientation-dependent electrostrictive and pseudo-piezoelectric responses arise from the long-range migration of oxygen vacancies, governed by direction-dependent migration difficulty under electric fields. This work provides direct evidence linking giant electromechanical responses with long-range oxygen-vacancy migration, and highlights that such effects in SC-YSZ cannot be neglected when employed as substrates or composite layers in electroactive materials and device systems.