Effect of B-site substitution on the stability of La0.2Sr0.8Fe0.8B0.2O3−, B = Al, Ga, Cr, Ti, Ta, Nb

Abstract

Single phase, cubic perovskites of composition La 0.2 Sr 0.8 Fe 0.8 B 0.2 O 3−δ , B = Al, Ga, Cr, Ti, Ta and Nb, were prepared by spray pyrolysis from aqueous precursor solutions. The effect of B-site substitution on the stability in a H 2 containing atmosphere was investigated using temperature programmed reduction (TPR). High temperature X-ray diffraction (HT-XRD) was performed under conditions similar to those in the TPR experiments. La 0.2 Sr 0.8 FeO 3−δ forms a brownmillerite-type anion-deficient ordered perovskite upon reduction at T ≈ 500• C. B-site substitution suppresses oxygen vacancy ordering, maintaining a perovskite structure under the above reducing conditions up to T ≈ 700• C. Trends in the kinetics of decomposition of B-site substituted La 0.2 Sr 0.8 FeO 3−δ are discussed.

La0.2Sr0.8Fe0.8Ta0.2O3−δ based thin film membranes with surface modification for oxygen production

“…MIEC membranes were prepared using La 0.2 Sr 0.8 Fe 0.8 Ta 0.2 O 3- (abbreviated in further text as LSFT2882) powder obtained from spray pyrolysis [10,11]. Porous substrates were made by uniaxially pressing ~3 mm thick discs of LSFT2882 powder with 20 wt.% carbon black addition 4 as a pore former.…”

“…This perovskite system was chosen due to its promising apparent stability behaviour which was observed during temperature programmed reduction tests [10]. Dense 20 µm thick membranes were prepared on porous support and deposition of a functional layer with pore former was done.…”

Catalytic combustion of methane by perovskite-type oxide nanoparticles as pollution prevention strategy

“…By considering the unsubstituted LaFeO 3 perovskite, the TPR profile shows only one peak with the onset at high temperature, that is 900 • C. That peak is related to the hydrogen consumption for the reduction of Fe 3+ to Fe 0 leading to the formation of metal iron and lanthanum oxide La 2 O 3 . On the other hand, by considering the Sr-substituted LaFeO 3 perovskite, the TPR profile shows peaks with the onset at low, intermediate and high temperatures, that are 200 • C, 500 • C and 700-800 • C. The first peak is associated to the reduction of Fe 4+ to Fe 3+ with the concomitant loss of lattice oxygen in order to maintain the charge neutrality, as confirmed by XRD analyses and Mossbauer spectra [24,25]. The lattice oxygen is easily expelled with the simultaneous reduction to Fe 3+ because the electrons provided from oxygen vacancy in agreement with the reaction O x O =1/2O 2(g) +V ·· O +2e − fill the d state of iron ions.…”

“…ions is confirmed by TPR analysis, fig.9. Since La 3+ and Sr 2+ are not reducible under the TPR operating conditions, all peaks in TPR profiles are related to the reduction steps of the iron ions [24][25][26][27]. By considering the unsubstituted LaFeO 3 perovskite, the TPR profile shows only one peak with the onset at high temperature, that is 900 • C. That peak is related to the hydrogen consumption for the reduction of Fe 3+ to Fe 0 leading to the formation of metal iron and lanthanum oxide La 2 O 3 .…”

“…The peak area growths up with increasing the amount of Sr 2+ because of the increase in the amount of Fe 4+ . The second peak is associated to the reduction of a certain amount of Fe 3+ to Fe 0 with the formation of the Ruddlesden-Popper type perovskite La 2−x Sr x Fe(III)O 4 , besides SrO and iron metal [24,25]. The last FIGURE 12.…”