Gd0.2Ce0.8O1.9/Y0.16Zr0.84O1.92 nanocomposite thin films for low temperature ionic conductivity. (September 2019)

• Record Type: Journal Article
• Authors: Perin, Giovanni; Gadea, Christophe; Rosa, Massimo; Sanna, Simone; Xu, Yu; Kiebach, Ragnar; Glisenti, Antonella; Esposito, Vincenzo
• Is Part Of: Journal of physics and chemistry of solids. Volume 132(2019)
• Page Start: 162
• Page End: 171
• Publication Date: 2019-09
• Subjects: Yttrium-stabilized zirconia -- Gadolinium doped ceria -- Nanocomposite -- Ionic conductivity -- Thin film; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2019.04.019
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Gd0.2 Ce0.8 O1.9 /Y0.16 Zr0.84 O1.92 (GDC/YSZ) nanocomposite is synthesized by a novel hybrid chemical route, where colloidal crystalline GDC nanoparticles from continuous hydrothermal synthesis are dispersed into a metalorganic YSZ matrix precursor. The result is a mixture of metal oxides in which GDC nanoparticles are finely distributed in a continuous metalorganic polymeric matrix to be crystallized after calcination. The GDC nanoparticles reduce the temperature necessary to obtain crystalline YSZ, which is already formed at 400 °C. The nanocomposite reveals structural stability up to 800 °C when treated in both air and reducing atmosphere, showing the onset of diffusion below 1000 °C. The diffusional processes are largely dependent on the nanometric grain size, with Zr 4+ diffusing abruptly towards GDC in air at 1000 °C and GDC/YSZ interdiffusion being hindered in reducing environment despite the onset temperature of 900 °C. The nanocomposite precursor is an inkjet-printable reactive water-based material, suitable for the deposition of thin films with a thickness below 100 nm after calcination at 750 °C. The crystal structure of the film reveals no interaction between GDC and YSZ but a microstrain (0.3% tensile strain for YSZ). The thin film microstructure shows a compact layer with 94% density. The nanocomposite shows high oxygen ionic conductivity at low temperatures (>5⋅10 -3 S⋅cm -1 at 500 °C), low activation energy (0.55 eV), and dominant oxygen ionic conductivity even in reducing conditions (pO2 < 10 – 25 atm). We show that these properties arise from the large interface between the components of the composite, due to the embedding of the GDC nanoparticles in the YSZ matrix, while ZrO-CeO intermixing can be avoided and no n-type conductivity is observed even at low oxygen activities and high temperatures. Highlights: A novel hybrid synthesis method is adopted for realizing a GDC/YSZ nanocomposite keeping control on the stoichiometry. Nanometric GDC nanoparticles are uniformly embedded in the matrix, enhancing YSZ formation at low temperature. The resulting material does not show interdiffusion up to 900 °C. The GDC/YSZ nanocomposite displays low activation energy for ionic conductivity, higher conductivity than YSZ below 600 °C. No n-type conduction due to cerium reduction at low pO2 is observed.