Synthesis of anion-deficient layered perovskites, ACa[sub 2]Nb[sub 3-x]M[sub x]O[sub 10-x] (A = Rb, Cs; M = Al, Fe), exhibiting ion-exchange and intercalation. Evidence for the formation of layered brownmillerites, ACa[sub 2]Nb[sub 2]AlO[sub 9] (A = Cs, H)
- Indian Institute of Science, Bangalore (India)
Anion-deficient layered perovskite oxides of the formula, ACa[sub 2]Nb[sub 3-x]M[sub x]O[sub 10-x] (A = Rb, Cs; M = Al, Fe) for 0 < x [le] 1.0, possessing tetragonal structures similar to the parent ACa[sub 2]Nb[sub 3]O[sub 10], have been synthesized. The interlayer A cations in these materials are readily exchanged with protons in aqueous HNO[sub 3] to give the protonated derivatives, HCa[sub 2]Nb[sub 3-x]M[sub x]O[sub 10-x]; the latter are solid Bronsted acids intercalating a number of organic amines including aniline (pK[sub a] = 4.63). The distribution of acid sites in the interlaying region of HCa[sub 2]Nb[sub 2]MO[sub 9] inferred from n-alkylamine intercalation suggests that oxygen vacancies and Nb/M atoms are disordered in the ACa[sub 2]Nb[sub 2]MO[sub 9] samples prepared at 1100-1200[degrees]C. Annealing a disordered sample of CsCa[sub 2]Nb[sub 2]AlO[sub 9] for a long time at lower temperatures tends to order the Nb/Al atoms and oxygen vacancies to produce octahedral (NbO[sub 6/2])-tetrahedral (AlO[sub 4/2])-octahedral (NbO[sub 6/2]) layer sequence reminiscent of the brownmillerite structure. 22 refs., 7 figs., 5 tabs.
- OSTI ID:
- 6768383
- Journal Information:
- Chemistry of Materials; (United States), Vol. 6:7; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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ALUMINIUM OXIDES
STRUCTURAL CHEMICAL ANALYSIS
CALCIUM OXIDES
CESIUM OXIDES
HYDROGEN COMPOUNDS
IRON OXIDES
NIOBIUM OXIDES
RUBIDIUM OXIDES
ANNEALING
CHEMICAL PREPARATION
ION EXCHANGE
TETRAGONAL LATTICES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CALCIUM COMPOUNDS
CESIUM COMPOUNDS
CHALCOGENIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
HEAT TREATMENTS
IRON COMPOUNDS
NIOBIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
REFRACTORY METAL COMPOUNDS
RUBIDIUM COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
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360204 - Ceramics
Cermets
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