Publication date: 10th April 2024
Grain boundary (GB) mass transport, and GB chemistry exert a pronounced influence on both the performance and stability of electrodes for solid oxide cells used in sustainable energy conversion and storage devices. Previous oxygen isotope exchange for the state-of-the-art lanthanum strontium cobalt ferrite (LSCF6428) has revealed a significant enhancement of 4 orders of magnitude in the oxygen diffusivity along the grain boundary when compared to the bulk [1]. In this study, (LSCF6428) was again used as a model mixed ionic and electronic conducting (MIEC) oxide to investigate GB transport at both single and multi-grain length scales. Dense LSCF6428 samples were prepared by sintering pressed pellets at 1250°C and the enhanced grain boundary diffusion was demonstrated by isotope exchange experiments at 350 and 500°C. Atom probe analysis of the exchanged samples revealed distinct changes in the grain boundary composition in the chemically modified layer (CML) of two of the GBs including a decrease in the oxygen content by ~4 %. Thus the enhancement of oxygen diffusivity is attributed to the accumulation of oxygen vacancies at the GB region, but not necessarily at the GB core. In addition to this oxygen deficiency, there were accompanying changes in the cation composition. The boundaries were found to be enriched in Sr and have a matching deficiency in La. The B-site cations, Co and Fe, were found to be enriched in the GB region. This result differs from an earlier study of cation distributions at GBs in La0.8Sr0.2MnO3 by EELS [2] where the B-site cation was found to be depleted and both A-site cations enriched. It is noteworthy that, despite the general trends that can be observed, when studying several grain boundaries (GBs) in LSCF, varying levels of enrichment and deficiency were observed for each cation, emphasizing the differing chemistry of each GB. In addition to the host cations, strong Na segregation was detected at all the GBs examined, despite the low (ppm) level of this impurity in the bulk. The presence of such impurities could affect the space charge potential, subsequently influencing the composition evolution at the grain boundary, as reflected by the distribution of oxygen vacancies [3]. Finally, the study also demonstrates the difference between the crystallographic defined GB width (δ), of ≤ 1 nm, and chemically defined δ, of several nm. This discrepancy could introduce inaccuracies in the calculation of the GB diffusivity (Dgb) and the space charge potential (Φ0) of GBs.
The authors acknowledge the support of the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101017709 (EPISTORE).
nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.
Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.
International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.