Invited Presentation: Elastic Anomalies and Electromechanical Effects in Gd-Doped Ceria

We have recently reported that at room temperature thin films of Gd-doped ceria exhibits a very large electrostriction effect. Our measurements with glass(150 µm)\Cr(100 nm)\Ce_1-xGd_xO_2-x/2(500 nm)\Cr(100 nm) cantilevers demonstrate that the magnitude of the electromechanical effect strongly depends on the value of the in-plane compressive strain. Under a 60 kV/cm field at room temperature, strain-free films may generate stress in the range of 30-150 MPa, whereas the films with compressive strain of a few tenth of a % can generate stress in excess of 500 MPa. The electromechanical response persists till the frequency of at least 6 kHz, which excludes a possibility of macroscopic material transfer. Modulated in-situ EXAFS and XANES measurements indicate that the microscopic origin of the electromechanical response is related to rearrangement of the local environment of cerium rather than gadolinium ions. Electric field affects the equilibrium between locally distorted and undistorted Ce_Ce-V_O complexes, which is similar to the mechanism responsible for a number of previously described inelastic anomalies. The magnitude of the electrostriction effect exhibits a complicated dependence on the Gd-content and suggests that cerium-vacancy interaction facilitate the mechanical response whereas vacancy-vacancy interactions weaken it. Our findings confirm that the presence of Ce_Ce-V_O complexes is essential for electromechanical activity and elastic anomalies. Tailoring the electrostriction effect in doped or oxygen-deficient ceria may therefore be possible by a proper choice of dopant chemistry and concentration.