Magnesium-Doped Sr2(Fe,Mo)O6-δ Double Perovskites with Excellent Redox Stability as Stable Electrode Materials for Symmetrical Solid Oxide Fuel Cells

In this work, magnesium-doped Sr2Fe1.2Mg0.2Mo0.6O6-delta and Sr2Fe0.9Mg0.4Mo0.7O6-delta double perovskites with excellent redox stability have been successfully obtained. The physicochemical properties including: crystal structure properties, redox stability, thermal expansion properties in oxidizing and reducing conditions, oxygen content as a function of temperature and transport properties, as well as the chemical compatibility with typical electrolytes have been systematically investigated. The in situ oxidation of reduced samples using high-temperature XRD studies shows the crystal structure of materials stable at up to a high-temperature range. The in situ reduction and oxidation of sinters with dilatometer measurements prove the excellent redox stability of materials, with the thermal expansion coefficients measured comparable with electrolytes. The oxygen nonstoichiometry delta of compounds was determined and recorded in air and argon up to 900 degrees C. Sr2Fe1.2Mg0.2Mo0.6O6-delta oxide presents satisfactory values of electrical conductivity in air (56.2 S.cm(-1) at 600 degrees C) and reducing conditions (10.3 S.cm(-1) at 800 degrees C), relatively high coefficients D and k, and good ionic conductivity (cal. 0.005 S.cm(-1) at 800 degrees C). The stability studies show that both compounds are compatible with Ce0.8Gd0.2O1.9 but react with the La0.8Sr0.2Ga0.8Mg0.2O3-d electrolyte. Therefore, the magnesium-doped double perovskites with excellent redox stability can be potentially qualified as electrode materials for symmetrical SOFCs and are of great interest for further investigations.

Automated summary

Magnesium-doped double perovskites with excellent redox stability were successfully obtained in this study. The physicochemical properties of these materials were systematically investigated, showing potential for application as electrode materials in symmetrical SOFCs.