Seminar LMGP 22.07.2025 - Simon Vernier

Simon Vernier

LMGP, Grenoble INP, UGA, CNRS

Optimised YSZ thin-film electrolytes with low yttria content via Metal-Organic Chemical Vapour Deposition for solid oxide cells

Abstract

The high ionic conductivity and good mechanical properties of yttria-stabilised-zirconia (YSZ) make it the most studied and widespread electrolyte used in solid oxide cells (SOCs). Thin film-based devices represent an attractive alternative to conventional high temperature SOCs and could provide in the future relatively low temperature operation (< 500 °C) with good efficiency [1]. When decreasing the electrolyte layer thickness, it can be interesting to lower the yttria content of the film from 8YSZ (8 _mol% Y₂O₃) to 3YSZ (3 _mol% Y₂O₃) to increase its mechanical flexibility [2]. However, this decrease is expected to result in a phase change and in a loss of ionic conductivity [3]. This work, intends to overcome this limitation by optimising the deposition conditions to find the best compromise between mechanical stability and ionic conductivity for such thin YSZ layers (tens to hundreds of nanometres).

Pulsed Liquid Injection Metal-Organic Chemical Vapour Deposition (PLI-MOCVD) was used to deposit 4YSZ, 6YSZ and 8YSZ thin films with thickness ranging from 40 nm to 800 nm. Many deposition parameters, such as the temperature, the precursor flow rate, the yttria content or the presence of remote plasma have been modified to obtain optimised polycrystalline, dense, pinhole-free layers. The morphological properties and chemical composition of the YSZ films deposited on several substrates have been investigated using SEM, (GI)XRD, TEM, and EPMA, and allowed to confirm the targeted dense and polycrystalline nature of the layers for 4YSZ and 6YSZ. The films present a mixture of cubic and tetragonal YSZ grains of different sizes depending on the precursor flow rate. However, films with a high Y₂O₃ substitution (≥8YSZ) did not present a dense morphology for the studied deposition conditions. Both in-plane and across plane ionic conductivities of the material have been measured by electrochemical impedance spectroscopy for the dense films. The results indicate that the 4YSZ films present a high ionic conductivity, similar to what is expected from bulk 8YSZ samples and slightly higher for 6YSZ. The YSZ films deposited by MOCVD presented in this work could therefore be used as thin film electrolytes, instead of the more usual 8YSZ, benefiting from their expected better mechanical behaviour.

1] Lee, Y. H. et al. Nano Lett. 20, 2943–2949 (2020).

[2] Won, B. R et al. J. Eur. Ceram. Soc. 42, 5813–5819 (2022).

[3] Duan, H. et al. ACS Comb. Sci. 15, 273–277 (2013).

[4] Navickas, E et al. J. Electrochem. Soc. 159, B411–B416 (2012).

[5] Navickas, E. et al. Solid State Ionics 211, 58–64 (2012).

[6] Joo, J. & Choi, G.. Solid State Ionics 177, 1053–1057 (2006).
 

Short Bio/CV

Graduated in 2022 from a master in material science and chemistry (Université de Tours) specialised in new energy technologies. Currently in the final year of his PhD.