Development and characterisation of dense lanthanum-based perovskite oxygen-separation capillary membranes for high-temperature applications

• Comparison of La0.6Sr0.4Co0.2Fe0.8O3−δ and Co-free, B-site substituted hollow fibres.
• In order of oxygen permeation flux values: LSCF6428>LSFZ2891>LSF551>LSFN2882.
• Great mechanical/chemical stability, uniform distribution of constituent elements.
• Optimised spinning and sintering method, applicable on wide range of MIEC membranes.

This research showcases the successful optimisation of the membrane fabrication process for a selection of lanthanum-based perovskite powders. A comparison is drawn between membranes made of LSCF and three of its cobalt-free analogues. Cobalt-free membranes have not been the subject of academic research to the same degree as LSCF and there have not been any reports of them being made into hollow fibre (capillaries). The present study examines how membrane performance is affected by the properties of the starting powders and the spinning and sintering parameters. In addition, it is proposed that the spinning and sintering method for hollow fibre fabrication described herein is applicable on an extensive range of MIEC materials for emerging oxygen perm-selective membrane-based technologies.This paper brings together characterisation work based on thorough pre- and post-operation SEM-EDS/EPMA-WDS analyses of the thermal and mechanical properties of the membranes including structural characterisation (XRD). The membranes were subjected to high temperature cycling (between 750 and 950 °C) and oxygen chemical potential differences for an average operation period of up to 10 days per sample. Despite the fact that oxygen permeation measurements showed that only LSCF membranes could achieve a greater magnitude of oxygen fluxes, all membranes exhibited great chemical and mechanical stability with uniform distribution of integral perovskite elements and no foreign elements. These La-based membranes hold potential to be integrated into modules and exploited in both existing and envisaged industrial processes and commercial applications.