title: High temperature structural study of Gd-doped ceria by synchrotron X-ray diffraction (673 K ≤ T ≤ 1073 K).
abstract: The crystallographic features of Gd-doped ceria were investigated at the operating temperature of solid oxides fuel cells, where these materials are used as solid electrolytes. (Ce(1-x)Gd(x))O(2-x/2) samples (x = 0.1, 0.3, 0.5, 0.7) were prepared by coprecipitation of mixed oxalates, treated at 1473 K in air, and analyzed by synchrotron X-ray diffraction in the temperature range 673 K ≤ T ≤ 1073 K at the Elettra synchrotron radiation facility located in Trieste, Italy. In the whole temperature span a boundary was found at x ∼ 0.2 between a CeO2-based solid solution (for x ≤ 0.2) and a structure where Gd2O3 microdomains grow within the CeO2 matrix, taking advantage of the similarity between Gd(3+) and Ce(4+) sizes; the existence of the boundary at x ∼ 0.2 was confirmed also by measurements of ionic conductivity performed by impedance spectroscopy. Similar to what observed at room temperature, the trend of the cell parameter shows the presence of a maximum; with increasing temperature, the composition corresponding to the maximum moves toward lower Gd content. This evidence can be explained by analyzing the behavior of the coefficient of thermal expansion as a function of composition.
authors.affiliation: DCCI, Department of Chemistry and Industrial Chemistry, University of Genova , Via Dodecaneso 31, 16146 Genova, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Artini
authors.forename: Marcella
authors.initials: M
authors.lastname: Pani
authors.forename: Andrea
authors.initials: A
authors.lastname: Lausi
authors.forename: Roberto
authors.initials: R
authors.lastname: Masini
authors.forename: Giorgio A
authors.initials: GA
authors.lastname: Costa