Interface Solid-State Reactions in La_0.8Sr_0.2MnO₃/Ce_0.8Sm_0.2O₂ and La_0.8Sr_0.2MnO₃/BaCe_0.9Y_0.1O₃ Disclosed by X-ray Microspectroscopy

Abstract

The stability of the electrode/electrolyte interface is a critical issue in solid-oxide cells working at high temperatures, affecting their durability. In this paper, we investigate the solid-state chemical mechanisms that occur at the interface between two electrolytes (Ce0.8Sm0.2O2, SDC, and BaCe0.9Y0.1O3, BCY) and a cathode material (La0.8Sr0.2MnO3, LSM) after prolonged thermal treatments. Following our previous work on the subject, we used X-ray microspectroscopy, a technique that probes the interface with submicrometric resolution combining microanalytical information with the chemical and structural information coming from space-resolved X-ray absorption spectroscopy. In LSM/BCY, the concentration profiles show striking reactive phenomena at the interface with a variety of micrometer-sized secondary phases: in particular, X-ray absorption spectra reveal at least three different chemical states for manganese (from +3 to +6). Also in LSM/SDC, a couple previously reported as chemically stable, we found the formation of small islets of SmMnO3 after the migration of manganese to the SDC side; these may constitute the nuclei for the subsequent formation of an interfacial resistive layer after more prolonged operation. The ability of manganese to adopt several oxidation states and crystal chemical environments is indicated as a possible cause for these behaviors.

Water Electrolysis toward Elevated Temperature: Advances, Challenges and Frontiers

“…In addition to the H 2 O-induced degradation, the electrode delamination, cation interdiffusion , and degradation associated with contaminants also lead to the deterioration of oxygen electrode materials. After operating for 100 h under the high steam concentration of 40% H 2 O, a sharp increase of the polarization resistance was revealed by the BCFZY electrode due to the delamination, which can be effectively alleviated by introducing a GDC interlayer between the electrolyte for enhanced adherence .…”

Figure‐of‐Merit Compatibility of Solid Oxide Fuel Cells

“…Reproduced with permission. [ 34 ] Copyright 2019, American Chemical Society. d) EDS scan from an electrolyte–electrode interface and real‐time plots of the phases’ fractions in electrode–electrolyte mixture acquired through a neutron diffraction.…”

“…An EDS line‐scan analysis can be a good way to examine the chemical distribution along the surface of the electrode. Some examples of the line‐scan analysis were carried out on the interface of lanthanum strontium manganite (LSM)‐based cathode at the BaCe 0.9 Y 0.1 O 3 electrolyte after 72 h of annealing which shows barium interdiffusion on the LSM cathode (Figure 4c) [ 34 ] and the analysis of cathode surface after sulfur poisoning in dry and wet conditions ( Figure 4d ) . [ 35 ] With a scan analysis, one can predict a possible secondary‐phase growth that may occur during the SOFC operation process at high temperature in some various condition.…”

Interface Diffusion and Compatibility of (Ba,La)FeO3−δ Perovskite Electrodes in Contact with Barium Zirconate and Ceria

“…One of the key points for fabricating a performant SOFC or PCFC is the compatibility between cathode and electrolyte. , The relatively high operational temperature often leads to degradation of the materials involved, such as cation demixing, atomic species segregation, and secondary phases. − These processes can strongly influence cell performance, since insulating phases can form, decreasing the ionic and electronic conductivity across the cell. When cation interdiffusion leads to the formation of new phases (the classical example is La 2 Zr 2 O 7 in SOFC at the contact between LSM and YSZ), this is often detrimental as the new structure typically has inferior transport properties, and may also cause problems arising from volume changes or differences in thermal expansion.…”

“…We first applied X-ray microspectroscopy to study the chemical and structural compatibility between various oxide materials for electrolytes (either proton- or oxygen-conducting) and oxygen electrodes such as (La,Sr)­(Fe,Co,Cu)­O 3−δ . ,,− Recent applications of more conventional techniques (both X-ray diffraction and electron microscopy) were reviewed . X-ray fluorescence (XRF) with a hard X-ray synchrotron beam has also been used recently to follow interdiffusion at the micrometer scale across a GDC interlayer between the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 oxygen electrode and YSZ electrolyte …”