Synthesis of oxide-based materials with a brownmillerite structure of the CaO‒Bi2O3‒Fe2O3 system

2020 ◽  
pp. 36-40
Author(s):  
N. A. Lomanova
Keyword(s):  
Brownmillerite Structure

Laser deposition of brownmillerite-structure Sr1.8La0.2GaFeO y thin films

2007 ◽  
Vol 43 (10) ◽  
pp. 1128-1133
Author(s):  
V. N. Varakin ◽  
S. P. Kabanov ◽  
G. M. Kaleva ◽  
E. D. Politova
Keyword(s):  
Thin Films ◽  
Laser Deposition ◽  
Brownmillerite Structure

Elastic Properties of Calcium Oxide Perovskites

2002 ◽  
Vol 718 ◽  
Author(s):  
Nancy L. Ross ◽  
Ross J. Angel ◽  
Jennifer Kung ◽  
Tracey D. Chaplin
Keyword(s):  
High Pressure ◽  
Bulk Modulus ◽  
Calcium Oxide ◽  
Specific Volume ◽  
Equations Of State ◽  
X Ray Diffraction ◽  
X Ray ◽  
Threefold Increase ◽  
Volume Relationship ◽  
Brownmillerite Structure

AbstractThe equations of state and axial moduli of the CaBO3 perovskites (B=Zr,Sn,Ti,Ge) and CaFeO2.5 with the brownmillerite structure have been determined using high-pressure, singlecrystal X-ray diffraction. The bulk modulus-specific volume relationship for the Ca-perovskites is nonlinear, with CaSnO3 and CaZrO3 displaying anomalous stiffening (higher bulk moduli) than previously reported and predicted [1,2]. The axial moduli of the a- and c-axes decrease steadily by ∼30% from the least-distorted of the Pbnm perovskites, CaGeO3, to the most distorted, CaZrO3, while the b-axis shows little change. The net result is a threefold increase in the anisotropy of the axial moduli of CaSnO3 and CaZrO3 (∼21%) relative to CaGeO3 and CaTiO3 (∼4-8%). The bulk modulus of CaFeO2.5 falls significantly below the trend for the stoichiometric perovskites. The introduction of 1/6 vacancies on the oxygen positions softens the perovskite structure by 25%.

scholarly journals Overlooked cation-ordered brownmillerite in Ba2(In1-xGax)2O5

2014 ◽  
Vol 70 (a1) ◽  
pp. C51-C51
Author(s):  
Christophe Didier ◽  
John Claridge ◽  
Matthew Rosseinsky
Keyword(s):  
Crystal Structure ◽  
Photocatalytic Activity ◽  
Ionic Conductivity ◽  
Structural Disorder ◽  
Size Difference ◽  
X Ray ◽  
Oxygen Interstitial ◽  
Interstitial Defects ◽  
Combined Structure ◽  
Brownmillerite Structure

As Goodenough showed 20 years ago, [1] Ba2In2O5 undergoes a transition from brownmillerite to cubic perovskite at higher temperatures, where it becomes a good oxygen ionic conductor. Past studies on doping gallium onto the indium sites [2] showed that higher Ga contents decrease the temperature required for the disordering to occur, in accordance with a higher structural disorder on the B site. In this work, we have showed that past studies on Ba2(In1-xGax)2O5 have overlooked a special ordering for the Ba2InGaO5 composition. Combined structure refinements of neutron and X ray powder diffraction show that this material adopts a brownmilleite structure below 1200°C with a layered ordering of In and Ga. This is one of a few examples of such an ordering in the brownmillerite structure only due to size difference between the B cations. This ordering further stabilizes the brownmillerite crystal structure compared to other compositions at smaller Ga contents. As could be expected, such stronger ordering is detrimental to ionic conductivity. At 1300°C, the material disorders into a cubic perovskite structure, which was already observed in past studies. However this polymorph has an unreported red colour, which was unexpected for a material with no incompletely filled orbitals. Incorporation of oxygen interstitial defects, on the basis of conductivity versus variable oxygen experiments and spectroscopic measurements, could be at the origin of this colouration much like in TiO2. [3] Unfortunately photocatalytic activity for water splitting could not be tested due to the strong instability of this material towards water.

scholarly journals Electric properties of oxyfluorides Ba2In2O5−0.5x F x with brownmillerite structure

2013 ◽  
Vol 49 (1) ◽  
pp. 45-51 ◽  
Author(s):  
N. A. Tarasova ◽  
Ya. V. Filinkova ◽  
I. E. Animitsa
Keyword(s):  
Electric Properties ◽  
Brownmillerite Structure

Modulated Distribution of Differently Ordered Tetrahedral Chains in the Brownmillerite Structure

2002 ◽  
Vol 14 (4) ◽  
pp. 1818-1826 ◽  
Author(s):  
S. Lambert ◽  
H. Leligny ◽  
D. Grebille ◽  
D. Pelloquin ◽  
B. Raveau
Keyword(s):  
Brownmillerite Structure

Specific features of the formation of oxygen defects in the SrFeO2.5 ferrate with a brownmillerite structure

2002 ◽  
Vol 44 (11) ◽  
pp. 2063-2066 ◽  
Author(s):  
V. M. Zainullina ◽  
I. A. Leonidov ◽  
V. L. Kozhevnikov
Keyword(s):  
Oxygen Defects ◽  
Brownmillerite Structure

New Oxide-Ion Electrolytes

1990 ◽  
Vol 210 ◽  
Author(s):  
J.B. Goodenough ◽  
Y.S. Zhen
Keyword(s):  
Transport Properties ◽  
Oxygen Vacancies ◽  
Ion Conductivity ◽  
Oxide Ion Conductivity ◽  
Vacancy Ordering ◽  
First Order Transition ◽  
Long Range Ordering ◽  
Short Range Correlations ◽  
Brownmillerite Structure ◽  
Oxide Ion

AbstractStrategic considerations for the design of new O2--ion solid electrolytes are presented, and preliminary measurements of the oxide-ion conductivity σo = (B/T) exp (-EA/kT) and transport number tO = σO/σ are reported for several oxides with perovsldte-related structures. Ba2In2O5 exhibits a first-order transition at Tt ∼ 930°C from the brownmillerite structure to a cubic perovskite with disordered oxygen vacancies and fast O2-ion conduction. Ba3In2MO8 (M = Ce, Zr, or Hf) contains oxygen vacancies ordered into every second BO2 (001) plane. An octahedralsite preference of the disordered M(IV) cations makes incomplete the oxygen-vacancy ordering, so a high extrinsic σo with EA ∼ 0.6 eV is found for T ≤ 400 °C. The transport properties of Ba3In2ZrO8 at 400 °C are equivalent to those of the stabilized zirconias at 800 °C. BagIn6O17 consists of an intergrowth of (BaO)2 rocksalt and Ba3In3O7.5 oxygen-deficient perovskite layers. Although there is no evidence of long-range ordering of the oxygen vacancies, nevertheless an EA = 1.06 eV and transport properties equivalent to stabilized zirconia indicate retention of short-range correlations to at least 950 °C. Attempts to prepare Bag Y6O17 yielded a mixture of hexagonal Ba3Y4O9 and unidentified phases. An EA = 0.45 eV above a Tt=370 °C gives a remarkable O2--ion conductivity at temperatures T > Tt in both the mixed-phase and pure Ba3Y4O9 at temperatures T > 370 °C, but the samples are extremely hygroscopic.

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