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Influence of Point‐Defect Reaction Kinetics on the Lattice Parameter of Ce 0.8 Gd 0.2 O 1.9
Author(s) -
Kossoy Anna,
Feldman Yishai,
Korobko Roman,
Wachtel Ellen,
Lubomirsky Igor,
Maier Joachim
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200801162
Subject(s) - materials science , dopant , vacancy defect , crystallographic defect , kinetics , lattice constant , dissociation (chemistry) , lattice (music) , crystal structure , condensed matter physics , crystallography , chemistry , doping , physics , optoelectronics , quantum mechanics , diffraction , acoustics , optics
The kinetics of point‐defect association/dissociation reactions in Ce 0.8 Gd 0.2 O 1.9 and their influence on the crystal lattice parameter are investigated by monitoring thermally induced stress and strain in substrate‐ and self‐supported thin films. It is found that, in the temperature range of 100–180 °C, the lattice parameter of the substrate‐supported films and the lateral dimensions of annealed, self‐supported films both exhibit a hysteretic behavior consistent with dissociation/association of oxygen vacancy–aliovalent dopant complexes. This leads to strong deviation from linear elastic behavior, denoted in the authors' previous work as the “chemical strain” effect. At room temperature, the equilibrium state of the point defects is reached within a few months. During this period, the lattice parameter of the substrate‐supported films spontaneously increases, while the self‐supported films are observed to transform from the flat to the buckled state, indicating that formation of the dopant–vacancy complex is associated with a volume increase. The unexpectedly slow kinetics of establishing the defect equilibrium at room temperature can explain the fact that, depending on the sample history, the “observable” lattice parameters of Ce 0.8 Gd 0.2 O 1.9 , as reported in the literature, may differ from one another by a few tenths of a percent. These findings strongly suggest that the lattice parameter of the materials with a large concentration of interacting point defects is a strong function of time and material preparation route.