Facile and versatile deposition of oxygen-conducting electrolyte thin films by ultrasonic spray pyrolysis from aqueous solutions

Thin and dense, oxygen-conducting electrolyte films are essential for intermediate-
temperature reversible solid oxide electrolysis cells (rSOCs). Such films can be reliably fabricated using scalable thin-film deposition techniques, such as ultrasonic spray pyrolysis (USP). This work proposes an environmentally friendly, cost- and time-efficient USP deposition route for gadolinium-doped ceria (CGO) and yttria-stabilized
zirconia oxide (YSZ) electrolyte films. The deposition employs water as solvent, water- soluble metal nitrates as precursors, and it is free of organic chelating additives. The
absence of organic species from the precursor solution prevents residual carbon contamination, microstructural defects, and secondary phases that can otherwise compromise the films’ implementation in rSOCs. The deposition is systematically investigated using a design-of-experiments approach and subsequently refined to reduce processing time, while optimizing the film growth on scandium-stabilized zirconium oxide substrates. In a next stage, using the optimized deposition parameters, the electrolyte thin films are deposited onto alumina substrates for the characterization of their conductivity. At 700 °C, the 20 mol.% gadolinium-doped CGO film exhibits a conductivity of 3.1 mS cm-1, while the 8 and 3 mol.% yttria-doped YSZ films yield a conductivity of 0.9 and 0.4 mS cm-1 respectively. The functional performance of the CGO films is further validated in a symmetrical cell configuration,
where the incorporation of a CGO diffusion barrier successfully suppressed interfacial degradation and secondary phase formation at the electrode/electrolyte interface. These results demonstrate the suitability and versatility of the proposed USP process for producing functional electrolyte layers for solid oxide cells.