Investigation of the inner microstructure of composite materials during their densification by scanning electron microscopy – LSM:YSZ electrode case study

• Published in: Electrochimica acta Vol. 482; p. 143979
• Main Authors: Carda, Michal, Novák, Libor, Budáč, Daniel, Paidar, Martin, Bouzek, Karel
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2024
• Subjects: Composite material; In-situ; LSM; SEM; YSZ; YSZ; SEM; In-situ; Composite material; LSM
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2024.143979

•Applicability of SEM technique for in-situ high temperature techniques demonstrated.•Densification process of LSM:YSZ composite for up to 1 200 °C visualized in real-time.•Temperature dependent non-stoichiometric changes in LSM composition observed.•LSM:YSZ composite solid framework formed exclusively by LSM phase. An understanding of the high-temperature processes, such as sintering, remains a challenge despite its paramount importance, and has yet to be achieved by the scientific community. Scanning electron microscopy is a valuable technique for investigating morphological changes, including elemental composition, by means of an energy-dispersive X-ray detector associated with these processes, with high resolution in-situ. Historically, this technique has been limited to experiments conducted at ambient temperature. However, by integrating scanning electron microscopy with a MEMS® heating chip, this limitation can be overcome, enabling the study of solid-state processes at temperatures of up to 1 200 °C. This study demonstrates one potential application of in-situ scanning electron microscopy – the densification of La1-xSrxMnO3-δ : (ZrO2:Y2O3) composite. This material, employed as an oxygen electrode in solid oxide cells, exhibits a complex microstructure. Achieving a balance between effective particle interconnection, ensuring high electric conductivity, and efficient mass transport through its porous structure is crucial. A comprehensive understanding of microstructure and surface composition evolution during the sintering process is vital to addressing trade off when optimizing densification conditions. It was shown that the densification of La1-xSrxMnO3-δ : (ZrO2:Y2O3) composite occurs in two steps. At 900 °C a significant additional porosity emerged due to the La1-xSrxMnO3-δ phase shrinkage (densification). The main densification process at 1 150 °C then acts as a self-healing mechanism, leading to the formation of a well-interconnected microstructure. Interparticle ligament formation is exclusively induced by the La1-xSrxMnO3-δ phase. Notably, no common degradation processes, such as La2Zr2O7 formation, were observed under the experimental conditions employed. This study underscores the promise of scanning electron microscopy with a heating chip extension for in-situ investigations pertinent to various high-temperature technologies. [Display omitted]