Effect of oxygen defects blocking barriers on gadolinium doped ceria (GDC) electro-chemo-mechanical properties

Abstract

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 defect configuration on the electro-chemomechanical properties. This is achieved by tuning the oxygen defects blocking barrier density in polycrystalline gadolinium doped ceria with known oxygen vacancy concentration, Ce0.9Gd0.1O2-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-chemomechanical properties, we show that oxygen vacancy distribution in the materials play a key role in ceria electrostriction, overcoming the expected contributions from grain size and dopant concentration.

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

“…The nanometric gadolinium doped ceria (GDC) powders with composition Ce1−xGdxO2−δ where x = 0.05−0.3 were synthesized by the co-precipitation method, as described elsewhere [5] [8].…”

Electromechanical dopant–defect interaction in acceptor-doped ceria

“…16,17 Although governed by the Ce Ce ÀV O complex, the local configuration of an oxygen vacancy is a crucial feature controlling electrostriction in bulk ceria. 16,19 Literature reports of both computational and experimental studies demonstrate that the configuration of oxygen vacancies in the lattice strongly depends on dopant size and valence, i.e., electrostatic (attractive) and elastic (repulsive) interaction between the cation and vacancy. [20][21][22] Fig.…”

“…. 19 In cerium based oxides, not only grain boundary but also dopant-defect association, nanoclusters, dopant segregation, and residual pores all combined introduce the ion-blocking effect. 2,28 The temperature-dependent total electrical conductivity (s) is illustrated in Fig.…”

Electro-chemo-mechanical effect in Gd-doped ceria thin films with a controlled orientation

“…30 However, grain size is not directly related to electrostriction performances as reported in our recent work. 27 We show that the electrostrictive behavior of polycrystalline CGO ceramics depends on the vacancy congurations within the grain boundaries. For these reasons, a grain boundary-free material is needed to obtain a clear insight into the sole lattice distortion effect.…”

“…2,7,[17][18][19][20][21] At room temperature, doped ceria showed outstanding electromechanical properties due to local distortion in the vicinity of oxygen vacancies. 22 Studies carried out on Gddoped ceria (CGO) thin lms, [22][23][24][25][26] bulk 27,28 and membranes, [29][30][31] show an average electrostriction coefficient of M e z 6 Â 10 À18 (m 2 V À2 ), 22 which is comparable to that of state-of-the-art materials such as Pb(Mn 1/3 Nb 2/3 )O 3 (M e ¼ 2 Â 10 À18 m 2 V À2 ). 32 For classical electrostrictors, Newnham et al provided a relationship in which the logarithm of performances depends on (S/3), where S is the elastic compliance and 3 is the dielectric constant.…”