The role of oxygen defects on the electro-chemo-mechanical properties of highly defective gadolinium doped ceria

Abstract

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 (Ce1−xGdxO2−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 reveals that doping controls the configuration of oxygen vacancies in the samples. Unexpectedly, we observe that electromechanical activity is depends on oxygen vacancy configuration rather than on its nominal concentration. The primary creep at room temperature indicates a declining viscoelastic trend with increasing oxygen defects.

Electromechanically active pair dynamics in a Gd-doped ceria single crystal

“…These values are comparable to the polycrystalline CGO pellets previously reported 4,14,37,38 . Previous results indicate that the electrostriction effect is influenced by the blocking factor and vacancy clustering of the grain boundaries 4,38 . However, as the single crystal has a continuous lattice, the characterization here reported is not affected by structural variables and so it is ascribed solely to lattice distortions.…”

“…Figure 2 shows the sample electric field-induced strain (in p.p.m) for voltage frequencies from 0.15 Hz to 100 Hz. At 0.15 Hz Strain saturation and frequency relaxation are visible, as consistent with CGO ceramics 4,14,37,38 . Table 1 reports the electrostriction coefficient for the corresponding frequency.…”

Electromechanical dopant–defect interaction in acceptor-doped ceria

“…These properties are also investigated in bulk ceria and other oxygen defective fluorites (Bi 2 O 3Àd ), illustrating similar outcomes. [10][11][12][13][14][15] The atomistic origin of this uncommon behavior is associated with the presence of charge compensating oxygen vacancies (V O ) in the ceria lattice. 16,17 The V O creates an electroactive elastic dipole (Ce Ce ÀV O ) having a long bond length and six anomalous reduced (Ce Ce -O O ) bonds when compared to the bond length of undoped ceria, leading to the development asymmetric charge distribution and anisotropic local dipolar elastic field around the host lattice.…”

“…These properties are also investigated in bulk ceria and other oxygen defective fluorites (Bi2O3−δ), illustrating similar outcomes. 9,10,11,12,13,14 The atomistic origin of this uncommon behavior is associated with the presence of charge compensating oxygen vacancies (V O •• ) in the ceria lattice. 15,16 The…”

Trivalent Dopant Size Influences Electrostrictive Strain in Ceria Solid Solutions

“… 9 , 15 , 16 Two types of measurements reveal particularly striking anomalies: nanoindentation (NI) and electromechanical strain. Room-temperature NI measurements of Gd- and Sm-doped ceria ceramics revealed the presence of primary creep, 8 , 17 − 19 as well as dependence of calculated Young’s modulus on the unloading rate. It is important to note that for a material like ceria, in which dislocation movement at room temperature is not likely, primary creep deformation is a clear sign of viscoelastic (of which anelasticity is one example) behavior.…”