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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]

In this report, the effect of the cold sintering process (CSP) on the electro-chemo-mechanical properties of 10 mol% Gd-doped ceria (GDC) is investigated. High purity nanoscale GDC powder is sintered via a cold sintering process (CSP) in pure water followed by post-annealing at 1000 °C. The resultant ceramics exhibits high relative density (∼90 %) with a fine grain size of ∼100 nm. This sample illustrates comparable electrochemical properties at intermediate-high temperatures and electromechanical properties at room temperature to the material prepared via conventional firing, i.e., sintering in the air at 1450 °C. Moreover, a large creep constant, as well as a low elastic modulus and hardness, are also observed in the CSP sample. [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]

Some oxygen defective metal oxides, such as cerium and bismuth oxides, have recently shown exceptional electrostrictive properties that are even superior to the best performing lead-based electrostrictors, e.g. lead-magnesium-niobates (PMN). Compared to piezoelectric ceramics, electromechanical mechanisms of such materials do not depend on crystalline symmetry but on the concentration of oxygen vacancy ( V O ⋅ ⋅ ) in the lattice. In this work, we investigate for the first time the role of oxygen defects configuration on the electro-chemo-mechanical properties. This is achieved by tuning the oxygen defects blocking barrier density in polycrystalline gadolinium doped ceria with known oxygen vacancy concentration, Ce 0.9 Gd 0.1 O 2-δ, δ = 0.05. Nanometric starting powders of ca. ∼12 nm are sintered in different conditions, including field assisted spark plasma sintering (SPS), fast firing and conventional method at high temperatures. These approaches allow controlling grain size and Gd-dopant diffusion, i.e. via thermally driven solute drag mechanism. By correlating the electro-chemo-mechanical properties, we show that oxygen vacancy distribution in the materials plays a key role in ceria electrostriction, overcoming the expected contributions from grain size and dopant concentration. Image 1 [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]