Review on Ceramic Interphases by Transmission and Scanning Electron Microscopy

Abstract

The Focused Ion Beam (FIB) technique was used to prepare site-specific samples from interfacial regions of different solid oxide fuel cells assemblies. Transmission and Scanning Electron Microscopy on the FIB foils combined with Electrochemical Impedance Spectroscopy (EIS) allowed the characterization of the electrode/electrolyte interphases and the determination of its influence on the cell performance after longterm operation conditions. This work reviews two cases: on one hand, Ln 2 NiO 4+δ (Ln= La, Nd) cathodes deposited on both Y 0.08 Zr 0.92 O 1.96 and Ce 0.9 Gd 0.1 O 1.95 electrolytes, that react at 900 °C during the adhesion treatment and at temperatures higher than 650 °C during the EIS measurements. These samples present a reaction layer of 10 nm thickness, which contains elements of both phases and was found responsible of the cell performance degradation. On the other hand, La 0.4 Sr 0.6 Co 0.8 Fe 0.2 O 3-δ cathodes showed excelent performance on Ceria electrolytes, even after 1000 hours at operation conditions. In that case, the microscopic analyses of FIB foils showed a semi-coherent interphase growth.

Silica: ubiquitous poison of metal oxide interfaces

“…59,60 A large number of reviews on the use of microscopy for metal oxide based electrochemical systems are available. 61,62 Scanning probe microscopy offers information about surface morphology and ex situ scanning tunnelling microscopy (STM) is extensively used to study the surface chemistry and band structure of e.g. gas sensing relevant metal oxides SnO 2 , and In 2 O 3 .…”