The Improvement in Chemical Stability of Lanthanum Based-Chromite Perovskites and Dual-Phase Composites with an Integrated Approach
The main focus of the project was to enhance the chemical stability of the perovskites and accelerate the materials development process for ceramic-based gas membranes, especially Oxygen Transport Membranes (OTMs).
The novel integrated approach of the project includes computational thermodynamics and solid-state experimental designs to promote understanding about the correlations of involved parameters, including composition, temperature, and atmosphere. Owing to the use of computational thermodynamics, a wide range of conditions could be examined as it could significantly speed up the process of materials design for ceramic membrane applications.
The project has been conducted in three levels: 1) Thermodynamics modeling on the chemical stability of the La-Sr-Cr-Fe-O system 2) Prediction for chemical stability and formations of secondary phases 3) Design and implement experiments based on thermodynamic simulations at elevated temperatures (>1000°C) and under atmospheric-controlled conditions.
Fig 1. Prediction in formations of secondary phases based on thermodynamics simulations results
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The knowledge for single perovskite systems has been also extended to design and develop advanced dual-phase composites with perovskite and fluorite phases. The thermodynamics simulations have been focused on the La-Sr-Cr-Fe-O-Y-Zr system as they can examine chemical interactions between two Lanthanum Based-Chromite perovskites and Yttria-stabilized Zirconia.
The use of the integrated approach of thermodynamics simulations helps to unravel new phenomena in the chemical stability of the La-Sr-Cr-Fe-O-Y-Zr system for OTM applications. The research sheds light on formations of new secondary phases, including spinel and corundum, and reports the formations of a liquid phase and second perovskite for the first time.
Fig 2. The formations of Spinel (in gold-color) and La2Zr2O7 (LZO) (in red-color) as secondary phases in (La, Sr)(Cr, Fe)O3-YSZ dual-phase composites.
The thermodynamics simulations have been backed up by extensive long-term experimental endeavors. The below video shows a semi-automatic XRD refinement cluster analysis on Perovskite-Fluorite (8YSZ) structure after exposure to OTM fabrication conditions (1400°C under reducing atmospheres).