Surface quality improvement of porous thin films suitable for nanoindentation

TL;DR

This paper investigates methods to improve the surface quality of porous LSCF thin films for reliable nanoindentation measurements, emphasizing ink self-levelling as a key factor for crack-free, smooth surfaces.

Contribution

It identifies ink self-levelling as crucial for surface quality improvement, enabling consistent nanoindentation of porous thin films.

Findings

Cracks and roughness are unaffected by deposition or sintering methods.

Self-levelling ink significantly reduces surface defects.

Improved surface quality leads to reliable nanoindentation data.

Abstract

The reliability of perovskite material LSCF to be used as cathode parts in solid oxide fuel cells also relies on its mechanical properties. Adequate surface conditions are desired when the as-sintered porous thin films are subjected to nanoindentation for mechanical property determination. In this study, extensive cracks and considerable surface roughness were found in the LSCF films after sintering at high temperatures. This would significantly scatter the nanoindentation data and result in unreliable measurements. Various attempts including the comparison of film deposition methods, drying and sintering processes, and reformulating the ink were made to improve the surface quality. Results revealed little dependence of cracking and surface roughness on deposition methods, drying or sintering processes. It was found that the critical factor for obtaining crack-free and smooth LSCF films was the ability of the ink to be self-levelling in the earlier wet state. Reproducible nanoindentation measurements were obtained for the films with improved surface quality.