Machine-learning prediction of thermal expansion coefficient for perovskite oxides with experimental validation.

Perovskite oxides have been of high-interest and relatively well studied over the last 20 years due to their various applications, specifically for solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). One of the key properties for a perovskite to perform well as a component in SOFCs, SOECs, and other high-temperature applications is its thermal expansion coefficient (TEC). The use of machine learning (ML) to predict material properties has greatly increased over the years and has proven to be a very useful tool for materials screening. The process of synthesizing and testing perovskite oxides is laborious and costly, and the use of physics-based models is often highly computationally expensive. Due to the amount of elements able to be accommodated in the ABO3 structure and the ability for crystallographic mixing in both the A and B-sites, there are a massive amount of possible ABO3 perovskites. In this paper, a ML model for the prediction of the TECs of AA'BB'O3 perovskites is produced and applied to millions of potential compositions resulting in reliable TEC predictions for 150 451 of the compositions.

Rapid and Low-Energy Fabrication of Symmetrical Solid Oxide Cells by Microwave Methods.

Solid oxide fuel cells are highly efficient, low-emission, and fuel-flexible energy conversion devices that can also run in reverse as solid oxide electrolysis cells, converting CO2 and/or H2O to useful fuels and pure O2. Our team has recently developed a highly promising mixed conducting oxide catalyst (La0.3Ca0.7Fe0.7Cr0.3O3-δ) that can be used at both the anode and cathode in either the fuel cell or electrolysis mode in a lower-cost symmetrical cell. However, there is still a need to improve material processing and cell manufacturing methods in this field. Here, we report, for the first time, fabrication of a symmetrical solid oxide cell, based on our very promising catalysts, using rapid, low-cost, low-energy, and green microwave (MW) processing techniques. These cells were fabricated with MW-sintered powders and were then MW-sintered without the use of any MW susceptors inside the electrode layers or any additional presintering steps. The catalyst layers show very stable nanostructures and do not delaminate, and the cells exhibit reaction rates that are similar to those obtained using normal ceramic processing methods. Importantly, the powder preparation and cell sintering steps, carried out using MW methods, require only ca. 1/3 and 1/9 of the time/energy, respectively, versus those required in traditional furnace methods, thus translating to significant cost savings.

Electrochemistry of La(0.3)Sr(0.7)Fe(0.7)Cr(0.3)O(3-δ) as an oxygen and fuel electrode for RSOFCs.

The use of a single porous mixed ion-electron conducting (MIEC) material as both the oxygen and fuel electrodes in reversible solid oxide cells is of increasing interest, primarily due to the resulting simplified cell design and lower manufacturing costs. In this work, La(0.3)Sr(0.7)Fe(0.7)Cr(0.3)O(3-δ) (LSFCr-3) was studied in a 3-electrode half-cell configuration in air, pure CO2 and in a 1 : 1 CO2 : CO mixture, over a temperature range of 650-800 °C. A detailed analysis of the impedance (EIS) data, under both open circuit and polarized conditions, as well as the cyclic voltammetry response of LSFCr-3 has shown that it is very active in all of these environments, but with oxygen evolution being somewhat more facile that oxygen reduction, and CO2 reduction more active than CO oxidation. Evidence for a chemical capacitance, associated with the Fe(3+/4+) redox process in LSFCr-3, was also obtained from the EIS and CV data in all gas environments.