Oxygen Permeation Properties of Partially A-Site Substituted BaFeO[sub 3−δ] Perovskites

Abstract

To explore oxygen permeable materials, oxygen permeation properties of partially A-site substituted BaFenormalO3−δ perovskites were investigated. Ba sites in BaFenormalO3−δ were substituted with cations such as Na, Rb, Ca, Y, and La by 5%. The partial substitution with Ca, Y, and La, whose ionic radii are smaller than that of Ba, succeeded in stabilizing a cubic perovskite structure that is a highly oxygen permeable phase, as revealed by X-ray diffraction analysis. This can be explained in terms of a decrease in the tolerance factor (t) . Among the normalBa0.95normalM0.05FenormalO3−δ (M = Na, Rb, Ca, Y, and La) membranes tested, normalBa0.95normalLa0.05FenormalO3−δ showed the highest oxygen permeability at 600–930°C, owing to the stabilization of the cubic phase without the formation of impurity phases. From chemical analysis, the oxygen permeability of normalBa1−xnormalLaxFenormalO3−δ membranes was correlated with the amount of oxygen defects (δ) in the lattice. The oxygen permeation flux of normalBa0.95normalLa0.05FenormalO3−δ membrane was significantly increased by reducing its thickness. Furthermore, a normalBa0.975normalLa0.025FenormalO3−δ membrane exhibited good phase stability under He flow at elevated temperatures. The obtained results indicate the promising properties of normalBa1−xnormalLaxFenormalO3−δ membranes as a cobalt-free material that has a high oxygen permeability, good phase stability, and low cost.

Design and experimental investigation of oxide ceramic dual-phase membranes

“…Among the developed materials, cobalt-doped Ln x (Ba,Sr,Ca) 1−x Co y Fe 1−y O 3−ı (Ln: rare earth metal, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1) usually have high oxygen permeation fluxes but are unstable under reducing environments and long-term operation at high temperatures [11][12][13][14][15][16][17][18][19][20]. Ln x (Ba,Sr,Ca) 1−x Fe y (Zn,Al,Ga,Ti,Zr,Ce) 1−y O 3−ı (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) usually possesses high stability under reducing environments but poor permeation fluxes [21][22][23][24][25][26][27][28][29][30][31]. Researchers have found that it is difficult to obtain a membrane material with high stability and permeation flux based on perovskite or perovskite-related structures [32,33].…”

Oxygen separation from air using Ba0.95La0.05FeO3− membranes fitted with porous La1−Sr FeO3− layers

“…The oxygen permeability through the membranes was measured using a flow apparatus previously reported [6,19]. The membrane was fixed to a quartz tube by welding with a silver ring at 960-965 o C. For permeation tests, synthetic air (200 cm 3 min -1 ) and He (150 cm 3 min -1 ) were flowed to each side of the membranes, respectively.…”

“…To improve the performance, we have been studying the membrane composition and structure. Recently, we have developed a new Fe-based membrane, La-doped BaFeO 3 (Ba 0.95 La 0.05 FeO 3-δ ) [6,7], which has higher oxygen permeation properties than conventional Cobased membranes such as La 1-x Sr x Co 1-y Fe y O 3-δ , SrCo 0.8 Fe 0.2 O 3-δ , and Sr 0.9 Ca 0.1 CoO 2.5+δ [8][9][10].…”

Oxygen permeation and coal-gas-assisted hydrogen production using oxygen transport membranes

“…Other candidate OTM materials are BaFeO 3Àd (BFO) perovskites that are partially substituted on the A-and B-sites. Others have studied the oxygen-permeation properties of partially substituted A-site [13] and B-site [14,15] BFO. Kida et al [13] suggested that the BFO membrane material has a phase transition from hexagonal or triclinic to cubic based on its oxygen-permeation properties.…”

“…Others have studied the oxygen-permeation properties of partially substituted A-site [13] and B-site [14,15] BFO. Kida et al [13] suggested that the BFO membrane material has a phase transition from hexagonal or triclinic to cubic based on its oxygen-permeation properties. Watanabe et al [14] also noted the phase transition and pointed out that it can be prevented by partial substitutions of A-site or B-site elements.…”