On the poisson ratio of thin films of Ce0.8Gd0.2O1.9 II: Strain-dependence

Natalia Goykhman, Yishay Feldman, Ellen Wachtel, Alex Yoffe, Igor Lubomirsky

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8 Citations (Scopus)

Abstract

We have adapted the X-ray diffraction technique of measuring crystal lattice parameters as a function of sample orientation in order to investigate the Poisson ratio (ν) of thin films of Ce0.8Gd0.2O1.9 with different degrees of in-plane compressive strain. Since Gd-doped ceria is mechanically inelastic, the unstrained lattice constant is not well-defined. Therefore in order to determine the Poisson ratio, more than one strain state of the same sample must be characterized. We have accomplished this with a home-built, diffractometer-compatible sample-bender. Using this device, we find that the Poisson ratio of as-deposited thin films of Gd-doped ceria is a decreasing function of the in-plane compressive strain. At total strain ≈ −0.9 %, ν is > 0.45, indicating that the material tends to preserve volume. Increase of the in-plane strain to ≈ −2 % produces a monotonic decrease in the Poisson ratio to ~0.2. Such low values are indicative of reduced volume. We explain this behavior by noting earlier results from our group suggesting that, at temperatures below 200 °C and at low strain values, Ce0.8Gd0.2O1.9 responds to non-isotropic mechanical stress by reorienting the locally distorted CeCe-VO –O7 units. At higher strain values this mechanism is apparently no longer effective. Measurement of the Poisson ratio of inelastic thin films by this technique is straightforward and not diffractometer-dependent. It therefore represents a practical method for ceramic thin film characterization.

Original languageEnglish
Pages (from-to)180-186
Number of pages7
JournalJournal of Electroceramics
Volume33
Issue number3-4
DOIs
Publication statusPublished - Dec 7 2014

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Keywords

  • Chemical strain
  • Gd-doped ceria
  • Thin films
  • XRD-strain measurements

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Mechanics of Materials
  • Electrical and Electronic Engineering
  • Materials Chemistry

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