Electrical conductivity and oxygen permeability of Ce_(0.8)Sm_(0.2)O_(2-δ)-PrBaCo_2O_(5+δ) dual-phase composites

摘要

A novel dual-phase oxygen permeation membrane based on ion-conducting Ce_(0.8)Sm_(0.2)O_(2-δ) (SDC) and mixed conducting PrBaCo_2O_(5+δ) (PBCO) is presented. There is no obvious reaction between the two phases under preparation and oxygen permeation conditions. The per-colative network of mixed conducting phase PBCO can be formed in SDC-PBCO composite when the ratio of PBCO is not less than 40 vol.%. Above this threshold, the oxygen permeability of SDC-PBCO membrane increases with increasing SDC content. Compared with pure PBCO membrane, the oxygen permeability of percolative SDC-PBCO composites is improved due to the 3D diffusion ability of SDC, which can shorten the tortuosity of the oxygen diffusion path in layered PBCO. The maximum oxygen flux based on 0.6-mm-thick SDC-PBCO (6/4) is 2.38 × 10~(-7) mol cm~(-2) s~(-1) at 925 ℃. The dependence of the oxygen permeation flux on the membrane thickness demonstrates that the bulk diffusion is the limiting step at thickness higher than 0.8 mm and the surface exchange may play an important role when the thickness is below that. Incorporation of SDC into PBCO can not only improve the oxygen permeability but also enhance the structural stability. The SDC-PBCO (6/4) dual-phase membrane is a promising candidate for oxygen separation application.