Ceramic Microstructure and Oxygen Permeability of SrCo ( Fe ,  M  )  O 3 − δ  (  M  = Cu or Cr )  Perovskite Membranes

Abstract

Stabilization of the cubic perovskite phase was demonstrated in the SrCo0.90_Fe0.10CrO3_0 oxide system at x 0.03. Oxygen permeability of SrCo(Fe, Cr)033 solid solutions was independent of chromium content at x =0.01-0.05. It was found that reducing ceramic grain size dimensions resulted in decreasing thermal expansion electrical conductivity, and oxygen permeability of SrCo(Fe, Cu)030 ceramic membranes. Oxygen transport through SrCo(Fe, M)03. ceramics was shown to be limited by both the bulk ionic conductivity and oxygen exchange currents. The limiting effect of the membrane permeate-side surface on the permeation was higher in comparison with that on the feed-side surface. IntraductionDense mixed ionic electronic conducting oxide membranes are of considerable interest for industrial processes such as oxygen separation, waste reduction and recovery, coal gasification, and selective oxidation of hydmcarbons.'9 The advan:age of mixed-conductive membranes lies in their infinite theoretical separation factor.'-3 For the oxidation processes, a promising feature is that the oxygen flux may alter the relative presence of different active oxygen species on the membrane surface, thereby providing higher selectivity for partial oxidation reactions.6-9 Moreover, it is possible to omit the preliminary step of purification of oxygen from air.2 Among the most promising groups of mixed conductors are the perovskitelike oxides having high ionic conductivity with a prevailing electronic conductivity.1012 Ceramic membranes of perovskite related oxide phases Sr(CoixFe,.)aOy (a = 1-20, x = 0-0.1) and La(Sr)Co(Fe)039 were used successfully in various extemal conditions.'1-'4 The highest oxygen permeation fluxes are characteristic of

Stability and oxygen transport properties of Pr2NiO4+δ ceramics

“…However, the oxygen fluxes through praseodymium nickelate membranes are still lower than those through most permeable materials such as Sr(Co,Fe)O 3−δ perovskites. 7 …”

“…6 The technique to study oxygen permeation using a solid-electrolyte cell with an oxygen pump and sensor was also described in previous work. 7 In terms of thermal pre-history of the membranes, the procedure included heating (3 • C/min) up to softening of a glass sealant (1115 • C), dwell for 5 min, and cooling down to 950 • C when the isothermal measurements were started. Further route included temperature cycling in the range 1023-950 • C, with steps of 50 • C and equilibration at each temperature.…”

Phase interaction and oxygen transport in La0.8Sr0.2Fe0.8Co0.2O3–(La0.9Sr0.1)0.98Ga0.8Mg0.2O3 composites

“…The oxygen ionic transport properties were evaluated using the measurements of steady-state oxygen permeation fluxes, as described elsewhere. 11 Only gas-tight samples were used for the permeation studies. All data on oxygen permeability presented in this work correspond to the membrane feed-side oxygen partial pressure (p 2 ) maintained at 21 kPa (atmospheric air); the permeate-side oxygen partial pressure (p 1 ) varied in range 0.2-20 kPa.…”

Interfacial Phenomena in Mixed Conducting Membranes: Surface Oxygen Exchange‐ and Microstructure‐Related Factors

“…However, other researchers argued that since the permeation experiments were performed under an air/helium gradient, the relatively low oxygen partial pressure at the membrane permeate side might lead to ordering of oxygen vacancies and to decreasing ionic conductivity [111], while small grains could contribute to stabilization of the disordered phase, as for bismuth vanadate-based materials [112]. For some materials such as SrCo(Fe,Cu)O 3Àd , the grain boundaries were reported to decrease transfer of oxygen anions [113]; thus, the larger the grain size, the higher the oxygen permeation flux through such membranes. Similar phenomena were reported by Wang et al [114] for Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3Àd (BSCF).…”