A protocol for characterizing relaxation of anisotropic strain in thin films of 10 mol% Eu- or Sm-doped ceria is described. The method is based on comparison of Raman spectra and X-ray diffraction patterns from substrate-supported films, displaying in-plane compressive strain (initial state), with analogous data from 2 mm diameter self-supported films (i.e., membranes), prepared by partial substrate removal (final state). These membranes are found to be relaxed, i.e., approximately unstrained, but with increased unit cell volume. The effective (i.e., 2-state) Grüneisen parameter of the F 2g Raman active mode for these films is calculated to be 0.4 ± 0.1, which is ≈30% of the literature value for the corresponding ceramics under isostatic pressure. On this basis, it is found that the observed red-shift of the F 2g mode frequency following isothermal strain relaxation of the doped ceria thin films cannot be determined solely by the increase in average unit cell volume. The study presented here may shed light on the suitability of Raman spectroscopy as a technique for characterizing strain in lanthanide-doped ceria thin films.
|Journal||Advanced Functional Materials|
|State||Published - 14 Mar 2019|
Bibliographical noteFunding Information:
This work was supported by the PAZY foundation and the Israeli Ministry of Science and Technology grant #3-12944. This research was also made possible in part by the historic generosity of the Harold Perlman Family. The authors would like to thank Dr. Yishay (Isai) Feldman for the assistance with the various XRD acquisition techniques. The corresponding author’s (O.K.) email address and the acknowledgments was updated on March 14th, 2019 after initial online publication.
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- Grüneisen parameter
- Raman spectroscopy
- anelastic relaxation
- doped ceria