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

TL;DR

This study introduces a novel nanocomposite thin film combining Gd0.2Ce0.8O1.9 and Y0.16Zr0.84O1.92 with high low-temperature ionic conductivity, structural stability, and suitability for thin film applications, advancing solid oxide electrolyte technology.

Contribution

It presents a new hybrid chemical synthesis method for GDC/YSZ nanocomposites with enhanced low-temperature ionic conductivity and thin film deposition capabilities.

Findings

High oxygen ionic conductivity (>5×10^-3 S/cm at 500°C)

Low activation energy (0.55 eV)

Stable microstructure up to 800°C

Abstract

Gd0.2Ce0.8O1.9/Y0.16Zr0.84O1.92 (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 {\deg}C. The nanocomposite reveals structural stability up to 800 {\deg}C when treated in both air and reducing atmosphere, showing the onset of diffusion below 1000 {\deg}C. The diffusional processes are largely dependent on the nanometric grain size, with Zr4+ diffusing abruptly towards GDC in air at 1000 {\deg}C and GDC/YSZ interdiffusion being hindered in reducing environment despite the onset temperature of 900 {\deg}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 {\deg}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 {\deg}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.