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Oxygen-deficient cerium oxide ceramics exhibit an anomalously high electromechanical response called giant electrostriction. This feature has been linked to the polarization and reorganization of ionic defects, i.e., V O · · , under an electric field. However, the exact mechanism and how it is related to intrinsic/extrinsic characteristics of doped ceria remains unclear. The present work investigates how alkaline-earth dopants with different defect–dopant interactions affect the overall electrochemical properties and defect chemistry and, ultimately, how these features impact the final electromechanical properties. We found higher dopant–defect associations attenuate the low-frequency relaxation of the electrostrictive coefficient. The defect chemistry is shown to be the main factor controlling the final electromechanical properties rather than defect concentration. All compositions show a similar electrostrictive response at high frequencies, indicating a common underlying mechanism. All samples showed a high electrostrictive coefficient (up to 3·10−17 m2/V2) and pseudo-piezoelectric response (32 pm/V). [Display omitted] [ABSTRACT FROM AUTHOR]

Recent investigations have shown that highly oxygen defective cerium oxides generate non-classical electrostriction that is superior to lead-based ferroelectrics. In this work, we report the effect of field-assisted spark plasma sintering (SPS) on electro-chemo-mechanical properties of calcium doped ceria (CDC). Nanometric powders of Ca. 10 nm are rapidly consolidated to form polycrystalline nanostructures with a high degree of crystalline disorder. Remarkably, the resultant material demonstrates a large electromechanical strain without a frequency-related relaxation effect. We conclude that electromechanical activity in CDC materials strictly depends on the Ca2+- V o ¨ interaction, while disorder at the crystalline boundaries has a minor effect. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Calcium/Gadolinium doped ceria ceramics were sintered via spark plasma sintering. • SPS produces dense sample, maintaining nano-scale grain sizes. • The sintering temperature in SPS tunes the electrical properties of the materials. • The ion-blocking effects and the activation energy depend on the dopant type. High purity nanoscale powders (~10–15 nm size) of two different compositions of ceria, doped with Gd3+ and Ca2+, have been consolidated by spark plasma sintering (SPS) at different temperatures. Fully-dense samples were observed only at a sintering temperature of 980 °C. The as-sintered samples showed rather fast grain growth with an average grain size below 300 nm. The electrical properties of the samples were evaluated by impedance spectroscopy over a wide range of temperatures (300–550 °C) in air. Electrical conductivity significantly enhanced with increasing sintering temperature. The compounds show an electrical blocking effect at the grain boundary, depending on the doping cations. [ABSTRACT FROM AUTHOR]

• Highly defective Gd-doped ceria (GDC) ceramics were sintered at 1450 °C for 10 h. • The Gd-content controls the configuration of oxygen vacancies. • The creep property and strain sensitivity are shown to decrease with Gd. • The electromechanical response is influenced by the ion-blocking barrier effect. In light of the recent discovery of giant electrostriction in defective fluorites, here we investigate the interplay between mechanical, electrochemical and electromechanical properties of oxygen defective ceria compositions (Ce 1−x Gd x O 2−δ) as the effect of Gd-doping (x = 0.05–0.3) at low temperatures. Highly dense polycrystalline ceramics are prepared as micron-size grains with a minimized grain boundary extent. Electrochemical ionic migration by impedance spectroscopy reveals that dopant content controls the oxygen vacancies association in the samples. Interestingly, we observe that electromechanical activity is strongly controlled by the local oxygen vacancy configuration rather than on its nominal concentration. The primary creep at room temperature indicates a declining viscoelastic trend with increasing oxygen defects. [ABSTRACT FROM AUTHOR]