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Showing papers on "Perovskite (structure) published in 2010"


Journal ArticleDOI
TL;DR: In the perovskite structure, B-site and A-site cations adopt different patterns of chemical order as discussed by the authors, and the tendency for A-site cations to order into layers stems from the bond strains that would result at the anion site if A and A′ cations of different sizes were to order with a rock salt arrangement.
Abstract: Although both A- and B-site cations have the same simple cubic topology in the perovskite structure they typically adopt different patterns of chemical order. As a general rule B-site cations order more readily than A-site cations. When cation ordering does occur, rock salt ordering of B/B′ cations is favored in A2BB′X6 perovskites, whereas layered ordering of A/A′ cations is favored in AA′B2X6 and AA′BB′X6 perovskites. The unexpected tendency for A-site cations to order into layers stems from the bond strains that would result at the anion site if A and A′ cations of different size were to order with a rock salt arrangement. The bonding instabilities that are created by layered ordering are generally offset either by anion vacancies or second order Jahn–Teller distortions of a B-site cation. Novel types of A-site cation ordering can be stabilized by a+a+a+ or a+a+c− tilting of the octahedra.

545 citations


Journal ArticleDOI
TL;DR: In this paper, the basic knowledge and recent advances in organic-inorganic perovskites are reviewed with particular emphasis on the feature work including: the novel -and -oriented perovsite structures, synthesis, film preparation, patterning methods and optoelectronic properties of hybrid pervskites.
Abstract: Organic–inorganic perovskites are a class of interesting compound in the perovskite family due to their unique structures of alternately stacking sheets of organic and inorganic components on the molecular scale. In this highlight, the basic knowledge and recent advances in organic–inorganic perovskites are reviewed with particular emphasis on the feature work including: the novel - and -oriented perovskite structures, synthesis, film preparation, patterning methods and optoelectronic properties of hybrid perovskites. Moreover, the small functional organic molecules can be templated into a regular arrangement by the inorganic perovskite framework. This unique material with nature-formed lamellar structure has the potential to be used as a template to create novel derivatives and bring about unique physical properties. Some interesting examples, such as intercalated polymer and silica network by topochemical polymerisation, fabrication of disk-like semiconductor nanocrystals and metal nanoparticles by hybrid perovskite templates are described.

540 citations


Journal ArticleDOI
TL;DR: In this article, a universal behavior in rare-earth (RE)-substituted perovskite BiFe0 3 is reported, where the structural transition from the ferroelectric rhombohedral phase to an orthorhombic phase exhibiting a double-polarization hysteresis loop and substantially enhanced electromechanical properties is found to occur independent of the rare earth dopant species.
Abstract: The discovery of a universal behavior in rare-earth (RE)-substituted perovskite BiFe0 3 is reported. The structural transition from the ferroelectric rhombohedral phase to an orthorhombic phase exhibiting a double-polarization hysteresis loop and substantially enhanced electromechanical properties is found to occur independent of the RE dopant species. The structural transition can be universally achieved by controlling the average ionic radius of the A-site cation. Using calculations based on first principles, the energy landscape of BiFe0 3 is explored, and it is proposed that the origin of the double hysteresis loop and the concomitant enhancement in the piezoelectric coefficient is an electric-field-induced transformation from a paraelectric orthorhombic phase to the polar rhombohedral phase.

350 citations


Journal ArticleDOI
TL;DR: In this paper, a review of the state-of-the-art in solid oxide fuel cells is presented, with an apparent tendency toward structures containing cations in lower coordination environments, particularly tetrahedral.
Abstract: In this review article, new systems being investigated for application in solid oxide fuel cells are discussed. For the electrode materials, materials with the perovskite or related structures continue to dominate the field, due to the need for high electronic conductivity. Research in this field is being directed toward compositions allowing high ionic conductivity in addition to their electronic contribution. In contrast, research on new electrolyte materials has shown a diverse range of structure-types, with an apparent tendency toward structures containing cations in lower coordination environments, particularly tetrahedral. In both the electrode and electrolyte area, materials allowing the incorporation of oxygen excess into interstitial sites have shown promising results, warranting further investigations of materials that will allow this type of defect chemistry.

327 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured the oxygen positions in LaNiO films to elucidate the coupling between epitaxial strain and oxygen octahedral rotations, and showed how strain systematically modifies both bond angles and lengths in this functional perovskite oxide.
Abstract: We have measured the oxygen positions in ${\text{LaNiO}}_{3}$ films to elucidate the coupling between epitaxial strain and oxygen octahedral rotations. The oxygen positions are determined by comparing the measured and calculated intensities of half-order Bragg peaks, arising from the octahedral rotations. Combining ab initio density-functional calculations with these experimental results, we show how strain systematically modifies both bond angles and lengths in this functional perovskite oxide.

281 citations


Journal ArticleDOI
TL;DR: This work presents a novel organic–inorganic hybrid cage compound (HIm)2[KFe(CN)6] (1; HIm = imidazolium) with a perovskite-type structure, in which the order– disorder behavior of the HIm polar guests give rise to striking dielectric anomalies.
Abstract: Progress in metal–organic framework (MOF) research has recently opened up new possibilities to realize hybrid materials with unique solid-state electric properties, such as ferroelectricity, piezoelectricity, and dielectricity. Compared with conventional pure inorganic/organic compounds, MOFs take advantage of structural tunability and multifunctionality to develop polarizable molecular materials with rich dielectric properties. Among them, switchable molecular dielectrics, which undergo transitions between high and low dielectric states, are promising materials with potential applications especially in data communication, signal processing, and sensing. However, reports of such MOFs have remained scarce owing to a lack of knowledge regarding control of the motions of the dipole moments in the crystal lattice. From the microscopic point of view, the tunable dielectric permittivity closely relates to the positional freedom of molecular dipole moments. For instance, polar molecules in the liquid state show larger dielectric permittivities than in the solid state owing to the “melting” and “freezing” of the molecular reorientations. With regard to MOFs, the dipole moments are rigidly fixed in the crystal structures in most cases, usually resulting in small and almost temperatureindependent dielectric permittivities. Fortunately, there is still much room for the integration of flexible units into the frameworks; that is, the introduction of a polarization rotation unit in the form of a solid-state molecular rotator or host–guest systems, such as porous compounds. Cage compounds, which are assembled by the inclusion of guest species into the well-matched host cages, is a very promising class of switchable molecular dielectrics. The reorientations of the polar guests in the carefully designed cage compounds may give rise to large dielectric permittivities, which are characterized by a multidimensional liquidlike state, and their freezing will lead to low-dielectric systems. Herein, we present a novel organic–inorganic hybrid cage compound (HIm)2[KFe(CN)6] (1; HIm = imidazolium) with a perovskite-type structure, in which the order– disorder behavior of the HIm polar guests give rise to striking dielectric anomalies. The (HIm)2[KFe(CN)6] crystals were grown from an aqueous solution of K3[Fe(CN)6] and (HIm)Cl salts by slow evaporation at room temperature as large red hexagonal plate perpendicular to the c axis. The existence of HIm and CN groups in 1 is verified by IR spectra. The CN group in 1 exhibits several vibrations in the range 2102–2143 cm , distinct from a single peak of 2118 cm 1 in K3[Fe(CN)6]. Thermal analysis reveals that 1 undergoes two phase transitions, at 187 K (T1) and 158 K (T2). For convenience, we label the phase above T1 as the high-temperature phase (HTP), the phase between T1 and T2 as intermediate-temperature phase (ITP), and the phase below T2 as low-temperature phase (LTP). Variable-temperature X-ray diffraction analysis reveals that 1 crystallizes in the centrosymmetric space group R3̄m at 293 K and 173 K as the HTP and ITP, respectively, and in C2/c at 83 K as the LTP. The common structural feature of the compound is the anionic cage formed by Fe CN K units in which the HIm cation resides. The metal–cyanide bond is strong and covalent in the fragment {Fe(CN)6} (Fe C = 1.9 ) and much weaker and ionic in the fragment {K(NC)6} (K N = 2.9 ; Figure 1). In the HTP, the cation reorients around the threefold c axis perpendicular to the ring plane. The cation consists of three carbon and two nitrogen atoms, which were all refined as carbon atoms. The five atoms of the

273 citations


Journal ArticleDOI
TL;DR: Temperature and excitation power dependance of the optical spectra gives a new insight into the excitonic and the phononic properties of this hybrid organic/inorganic semiconductor.
Abstract: We report on optical spectroscopy (photoluminescence and photoluminescence excitation) on two-dimensional self-organized layers of (C6H5C2H4-NH3)2-PbI4 perovskite. Temperature and excitation power dependance of the optical spectra gives a new insight into the excitonic and the phononic properties of this hybrid organic/inorganic semiconductor. In particular, exciton-phonon interaction is found to be more than one order of magnitude higher than in GaAs QWs. As a result, photoluminescence emission lines have to be interpreted in the framework of a polaron model.

247 citations


Journal ArticleDOI
TL;DR: Calculations on a model interfacial structure are reported which avoids chemical influences and show that the symmetry mismatch imposes an interfacial layer with distortion modes that do not exist in either bulk material, creating new interface properties driven by symmetry alone.
Abstract: Perovskite transition-metal oxides are networks of corner-sharing octahedra whose tilts and distortions are known to affect their electronic and magnetic properties. We report calculations on a model interfacial structure which avoids chemical influences and show that the symmetry mismatch imposes an interfacial layer with distortion modes that do not exist in either bulk material, creating new interface properties driven by symmetry alone. Depending on the resistance of the octahedra to deformation, the interface layer can be as small as one unit cell or extend deep into the thin film.

215 citations


Journal ArticleDOI
TL;DR: In this paper, a template engineering approach was proposed to match the alkaline-earth layer in the BaFe(2)As/oxygen layer of the BaTiO(3) template.
Abstract: Understanding new superconductors requires high-quality epitaxial thin films to explore intrinsic electromagnetic properties and evaluate device applications. So far, superconducting properties of ferropnictide thin films seem compromised by imperfect epitaxial growth and poor connectivity of the superconducting phase. Here we report new template engineering using single-crystal intermediate layers of (001) SrTiO(3) and BaTiO(3) grown on various perovskite substrates that enables genuine epitaxial films of Co-doped BaFe(2)As(2) with a high transition temperature (T(c,rho=0) of 21.5 K, where rho=resistivity), a small transition width (DeltaT(c)=1.3 K), a superior critical current density J(c) of 4.5 MA cm(-2) (4.2 K) and strong c-axis flux pinning. Implementing SrTiO(3) or BaTiO(3) templates to match the alkaline-earth layer in the Ba-122 with the alkaline-earth/oxygen layer in the templates opens new avenues for epitaxial growth of ferropnictides on multifunctional single-crystal substrates. Beyond superconductors, it provides a framework for growing heteroepitaxial intermetallic compounds on various substrates by matching interfacial layers between templates and thin-film overlayers.

213 citations


Journal ArticleDOI
TL;DR: The origin of the dielectric transition is attributed to the dynamics of the DMA cations: above 190 K these cations can rotate inside the cubooctahedral cavity created by the [Mn(HCOO)(3)](-) framework, while for lower temperatures such rotation gets frozen, and their cooperative arrangement inside the cavities give rise to the observed dielectrics transition.
Abstract: We have found that the hybrid organic-inorganic perovskite-like formate Mn(HCOO)(3)[(CH(3))(2)NH(2)] shows a dielectric transition around 190 K. According to single crystal X-ray diffraction, the compound shows rhombohedral symmetry at room temperature and monoclinic symmetry at low temperature (100 K), and the main difference between both structures is that the (CH(3))(2)NH(2)(+) (DMA) cations are disordered in the high temperature phase but cooperatively ordered in the low temperature one. The vibrational spectra of this compound reveal that significant changes take place in the vibrations ascribed to the DMA cation (changes in the frequency of certain vibrations, splitting of particular vibrations, and changes in the intensities), while no significant changes have been observed in those attributed to the formate anion. On the basis of all this information, we attribute the origin of the dielectric transition to the dynamics of the DMA cations: above 190 K these cations can rotate inside the cubooctahedral cavity created by the [Mn(HCOO)(3)](-) framework, while for lower temperatures such rotation gets frozen, and their cooperative arrangement inside the cavities give rise to the observed dielectric transition.

191 citations


Journal ArticleDOI
TL;DR: In this article, the A-site non-stoichiometry in Ba1−xZr0.8Y0.2O3−δ, a candidate electrolyte material for fuel cell and other electrochemical applications, was investigated.
Abstract: Recent literature indicates that cation non-stoichiometry in proton-conducting perovskite oxides (ABO3) can strongly influence their transport properties. Here we have investigated A-site non-stoichiometry in Ba1−xZr0.8Y0.2O3−δ, a candidate electrolyte material for fuel cell and other electrochemical applications. Synthesis is performed using a chemical solution approach in which the barium deficiency is precisely controlled. The perovskite phase is tolerant to barium deficiency up to x = 0.06 as revealed by X-ray diffraction analysis, but accommodates the non-stoichiometry by incorporation of yttrium on the A-site. The dopant partitioning can explain the decrease in cell constant with increasing x, the decrease in proton conductivity (the latter as measured by a.c. impedance spectroscopy under humidified atmosphere), and the decrease in grain size in the sintered compacts. Within the single-phase region barium deficiency also has a detrimental impact on grain boundary conductivity, as a result both of the decreased grain size, leading to a higher number density of grain boundaries and of an increased per boundary resistivity. At higher values of x, a two phase system is observed, with yttria appearing as the predominant secondary phase and the barium zirconate reverting to an undoped composition. From the relative concentrations of the observed phases and their lattice constants, the ternary phase behavior at 1600 °C (the sintering temperature) is generated. Both the bulk and grain boundary conductivities are sharply lower in the two-phase system than in the single phase compositions. The control over processing conditions demonstrates that it is possible to reproducibly prepare large-grained, stoichiometric BaZr0.8Y0.2O3−δ with a total conductivity of 1 × 10−2 Scm−1 at 450 °C, while revealing the mechanisms by which barium deficiency degrades properties.

Journal ArticleDOI
TL;DR: In this paper, the physicochemical and catalytic properties of a Ni/La2O3 catalyst obtained by reduction of a lanthanum nickelite, LaNiO3, with perovskite structure were investigated.
Abstract: The objective of the present work has been the study of the physicochemical and catalytic properties of a Ni/La2O3 catalyst obtained by reduction of a lanthanum nickelite, LaNiO3, with perovskite structure. The perovskite, obtained by means of a spray pyrolysis method, provides a Ni/La2O3 system active in different methane reforming reactions. The catalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-Ray photoemission spectroscopy (XPS), temperature-programmed reduction and oxidation (TPR, TPO) and catalytic activity tests. Although not evidenced by XRD data, XAS and TPR measurements show the presence of an amorphous NiO phase in the original sample, together with the crystalline LaNiO3 phase. Upon reoxidation treatment of the reduced Ni/La2O3 catalyst, the LaNiO3 structure is partly recovered which provides a convenient way to regenerate a waste catalyst (reoxidation and new reduction in hydrogen). The catalyst is active in several reactions of methane with oxygen, water and CO2, showing a remarkable stability specially under dry reforming of methane (DRM) reaction conditions. This quite great catalytic performance has been explained by the high resistance of the nickel particles to be oxidized, as detected by in situ XAS. In the presence of water, as in steam reforming of methane (SRM) reaction conditions, these metallic particles are gradually oxidized, which explains the linear decreasing of the catalytic performance observed for the SRM reaction.

Journal ArticleDOI
TL;DR: In this paper, the degradation behavior and mechanism of perovskite-type BaCo0.4Fe 0.4Nb0.2O3-δ membranes in CO2-containing atmospheres at 800−1000 °C were examined.
Abstract: This study investigates the degradation behavior and mechanism of perovskite-type BaCo0.4Fe0.4Nb0.2O3-δ membranes in CO2-containing atmospheres at 800−1000 °C and examines the influence of cation substitution on the CO2 resistance. The oxygen permeation flux deteriorates rapidly upon switching the sweep gas from Ar to CO2. During exposure to CO2, the membrane material decomposes to form a compact BaCO3 surface layer and a subjacent porous decomposed zone which consists of CoO and a Co-depleted Ba(Co, Fe, Nb)O3-δ perovskite phase. Within this zone, the composition of the perovskite product varies with depth, with more pronounced cobalt depletion found closer to the carbonate layer. The growth of the product layers is found to be diffusion-controlled and can be enhanced by the presence of oxygen. Outward diffusion of barium from the unreacted perovskite bulk appears to rate limit the growth. A drop of the barium chemical potential is concurrent with a larger degree of cobalt depletion in the Ba(Co, Fe, Nb)O...

Journal ArticleDOI
TL;DR: In this paper, an antiferroelectric (Pb0.97La0.02)-O3 (Zr1−x−ySnxTiy)O3 thin film with orthorhombic perovskite structure was prepared on Si substrates by a chemical solution deposition process and a secondary pyrochlore phase was revealed with transmission electron microscopy.
Abstract: Antiferroelectric (Pb0.97La0.02)(Zr1−x−ySnxTiy)O3 (PLZST) thin films with orthorhombic perovskite structure were prepared on Si substrates by a chemical solution deposition process. A secondary pyrochlore phase, which was not detectable with x-ray diffraction, was revealed with transmission electron microscopy. The pyrochlore phase was effectively suppressed by the introduction of polyethylene glycol (PEG) in the precursor solution and applying PbO capping layer on the surface of the films. With the persistent and detrimental pyrochlore phase removed completely, our PLZST antiferroelectric thin films exhibited excellent electrical and electromechanical properties. A large energy storage density up to 13.7 J/cm3 was exhibited from the polarization measurement, and a strain of 0.49% under the clamping of the substrate was also achieved in the thin film with high Zr content.

Journal ArticleDOI
TL;DR: Tong et al. as mentioned in this paper investigated the mechanisms for the rapid formation of the cubic perovskite phase of BZY, pellet densification, and grain growth during SSRS synthesis using a suite of experimental techniques.
Abstract: A cost-effective solid-state reactive sintering (SSRS) method has recently been developed to synthesize high quality, fully dense, and large-grained yttrium-doped barium zirconate (BZY) ceramic pellets from the raw materials of BaCO3, ZrO2, Y2O3, and NiO, resulting in total proton conductivities as high as 3.3 × 10−2 S·cm−1at 600 °C under a wet argon atmosphere [J. Tong et al., Solid State Ionics, 2010, 181, 496]. In the present work, the mechanisms for the rapid formation of the cubic perovskite phase of BZY, pellet densification, and grain growth during SSRS synthesis are investigated in detail using a suite of experimental techniques. The pre-reaction addition of NiO to the precursor powders is confirmed to accelerate the formation of the cubic perovksite BZYphase. The rapid and full densification of NiO-modified pellets at relatively low temperature (1350 °C) is ascribed to the formation of the impure phase BaY2NiO5 and its subsequent role as a sintering aid. The dramatic further grain growth after densification is facilitated by the partial decomposition of the BaY2NiO5 (which is located primarily at grain boundaries) and its incorporation into the cubic perovskite structure of BZY.

Journal ArticleDOI
TL;DR: In this paper, a microwave-assisted combustion method in air and employed as both anode and cathode in symmetrical solid oxide electrolysis cells (SOECs) for hydrogen production for the first time in this work.

Journal ArticleDOI
TL;DR: In this article, the Na 0.5 Bi 0.3 -K 0.25 -TiO 3 (NBT-KBT) system, with its complex perovskite structure, was investigated as a promising material for piezoelectric applications.
Abstract: We have investigated the Na 0.5 Bi 0.5 TiO 3 –K 0.5 Bi 0.5 TiO 3 (NBT–KBT) system, with its complex perovskite structure, as a promising material for piezoelectric applications. The NBT–KBT samples were synthesized using a solid-state reaction method and characterized with XRD and SEM. Room-temperature XRD showed a gradual change in the crystal structure from tetragonal in the KBT to rhombohedral in the NBT, with the presence of an intermediate morphotropic region in the samples with a compositional fraction x between 0.17 and 0.25. The fitted perovskite lattice parameters confirmed an increase in the size of the crystal lattice from NBT towards KBT, which coincides with an increase in the ionic radii. Electrical measurements on the samples showed that the maximum values of the dielectric constant, the remanent polarization and the piezoelectric coefficient are reached at the morphotropic phase boundary (MPB) ( ɛ = 1140 at 1 MHz; P r = 40 μC/cm 2 ; d 33 = 134 pC/N).

Journal ArticleDOI
TL;DR: In this article, defect reactions, water incorporation and proton-dopant association in cubic cubic BaZrO3 and orthorhombic BaPrO3 perovskite materials are investigated using well-established atomistic simulation techniques.
Abstract: Defect reactions, water incorporation and proton-dopant association in the BaZrO3 and BaPrO3 perovskite materials are investigated using well-established atomistic simulation techniques. The interatomic potential models reproduce the experimental cubic BaZrO3 and orthorhombic BaPrO3 structures. The high defect energies suggest that significant intrinsic disorder (either Frenkel, Schottky or reduction) in BaZrO3 is unlikely, which is consistent with the relative chemical stability of this system. In contrast, favourable redox processes are found for intrinsic reduction of BaPrO3, and oxidation of acceptor-doped BaPrO3, the latter leading to p-type conduction properties as observed experimentally. Binding energies for dopant-OH pairs in BaZrO3 indicate the weakest association for Gd and Y dopants, and the strongest association for Sc. The high binding energies for all the dopant-OH pair clusters in BaPrO3 suggest strong proton trapping effects, which would be detrimental to proton conductivity. The water incorporation or hydration energy is found to be less exothermic for BaZrO3 than for BaPrO3, the higher exothermic value for the latter suggesting that water incorporation extends to higher temperatures in accord with the available thermodynamic data. The energies and pathways for oxide ion migration in both materials are also investigated.

Journal ArticleDOI
TL;DR: In this paper, the decomposition of cubic perovskite-type oxide BaxSr1−xCo0.8Fe0.2O3−δ (BSCF) into hexagonal and cubic pervskite type phases has been examined by means of Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-Ray Diffraction (XRD) measurements, which reveal that the new hexagonal phase grows predominantly at the grain boundaries of BSC
Abstract: The decomposition of the cubic perovskite-type oxide BaxSr1−xCo0.8Fe0.2O3−δ (BSCF) into hexagonal and cubic perovskite-type phases has been examined by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED) and X-Ray Diffraction (XRD). SEM and TEM measurements reveal that the new hexagonal phase grows predominantly at the grain boundaries of BSCF ceramics and that the cation composition of the newly formed hexagonal phase differs from that of the starting material. An orientational relationship between the hexagonal and the parent cubic phase was also observed. By means of ex situ XRD the phase fraction of the hexagonal phase was determined as a function of annealing time. A kinetic analysis of the data, based on Avrami-type kinetics, indicates that the decomposition is independent of the initial A-site composition, and the obtained reaction order supports the conclusion that the hexagonal phase grows at the grain boundaries in dense ceramic samples.

Journal ArticleDOI
TL;DR: In this paper, the electrochemical properties of perovskite oxides deposited on the protonic electrolyte BaCe 0.9 Y 0.1 O 3−−− δ have been studied and the Area Specific Resistances have been measured under air/H 2 O (3%) atmosphere.

Journal ArticleDOI
TL;DR: In this article, a significant amount of iron in MgSiO 3 perovskite (Pv) is Fe 3+ (Fe 3+ /ΣFe = 10-60%) due to crystal chemistry effects at high pressure.

Journal ArticleDOI
TL;DR: In this article, a member of the hybrid perovskite family is shown to be an electrically polar and magnetic compound with dielectric anomaly around the Curie point (247 K).
Abstract: We demonstrate that ethylammonium copper chloride, (C2H5NH3)2CuCl4, a member of the hybrid perovskite family is an electrically polar and magnetic compound with dielectric anomaly around the Curie point (247 K). We have found large spontaneous electric polarization below this point accompanied with a color change in the sample. The system is also ferroelectric, with large remnant polarization (37??C/cm2) that is comparable to classical ferroelectric compounds. The results are ascribed to hydrogen-bond ordering of the organic chains. The coexistence of ferroelectricity and dominant ferromagnetic interactions allows to relate the sample to a rare group of magnetic multiferroic compounds. In such hybrid perovskites the underlying hydrogen bonding of easily tunable organic building blocks in combination with the 3d transition-metal layers offers an emerging pathway to engineer multifuctional multiferroics.

Journal ArticleDOI
TL;DR: The cubic perovskite Ba 0.5Sr0.5Co 0.8Fe 0.2O3−δ (denoted BSCF) is the state-of-the-art ceramic membrane material used for oxygen separation technologies above 1150 K as discussed by the authors.
Abstract: The cubic perovskite Ba0.5Sr0.5Co0.8Fe0.2O3−δ (denoted BSCF) is the state-of-the-art ceramic membrane material used for oxygen separation technologies above 1150 K. BSCF is a mixed oxygen-ion and electron conductor (MIEC) and exhibits one of the highest oxygen permeabilities reported so far for dense oxides. Additionally, it has excellent phase stability above 1150 K. In the intermediate temperature range (750−1100 K), however, BSCF suffers from a slow decomposition of the cubic perovskite into variants with hexagonal stacking that are barriers to oxygen transport. To elucidate details of the decomposition process, both sintered BSCF ceramic and powder were annealed for 180−240 h in ambient air at temperatures below 1123 K and analyzed by different transmission electron microscopy techniques. Aside from hexagonal perovskite Ba0.6Sr0.4CoO3−δ, the formation of lamellar noncubic phases was observed in the quenched samples. The structure of the lamellae with the previously unknown composition Ba1−xSrxCo2−yFey...

Journal ArticleDOI
TL;DR: In this article, a single-phase BaFe 0.5 Nb 0.3 O 3 (BFN) ceramics were prepared by solid-state reaction method and were characterized by X-ray Diffraction (XRD) technique.

Journal ArticleDOI
TL;DR: The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC and are attributed in part to higher oxygen nonstoichiometry.
Abstract: The active ingredient: La{sub 0.8}Sr{sub 0.2}CoO{sub 3-{delta}} (LSC) epitaxial thin films are prepared on (001)-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer. The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry.

Journal ArticleDOI
04 Nov 2010-ACS Nano
TL;DR: By creating a new, rather unexpected, and yet simple way to such a superlattice assembly of perovskite oxides, it is found that (LaNb( 2)O(7)/Ca(2)Nb (3) O(10)) super lattices possess a new form of interface coupling, which gives rise to ferroelectricity.
Abstract: Combining different materials into desired superlattice structures can produce new electronic states at the interface and the opportunity to create artificial materials with novel properties. Here we introduce a new, rather unexpected, and yet simple way to such a superlattice assembly of perovskite oxides: in the Dion−Jacobson phase, a model system of layered perovskites, high-quality bicolor perovskite superlattices (LaNb2O7)nL(Ca2Nb3O10)nC are successfully fabricated by a layer-by-layer assembly using two different perovskite nanosheets (LaNb2O7 and Ca2Nb3O10) as a building block. The artificially fabricated (LaNb2O7/Ca2Nb3O10) superlattices are structurally unique, which is not feasible to create in the bulk form. By such an artificial structuring, we found that (LaNb2O7/Ca2Nb3O10) superlattices possess a new form of interface coupling, which gives rise to ferroelectricity.

Journal ArticleDOI
TL;DR: In this paper, perovskite oxides with cubic phase were investigated as potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) on La 0.9 Nb 0.1 Ga 0.2 O 3− δ (LSGM) electrolyte.

Journal ArticleDOI
24 Aug 2010-ACS Nano
TL;DR: This work has successfully fabricated multilayer nanofilms directly on SrRuO3 or Pt substrates without any interfacial dead layers, providing a key for understanding the size effect and also represents a step toward a bottom-up paradigm for future high-κ devices.
Abstract: Size-induced suppression of permittivity in perovskite thin films is a fundamental problem that has remained unresolved for decades. This size-effect issue becomes increasingly important due to the integration of perovskite nanofilms into high-κ capacitors, as well as concerns that intrinsic size effects may limit their device performance. Here, we report a new approach to produce robust high-κ nanodielectrics using perovskite nanosheet (Ca2Nb3O10), a new class of nanomaterials that is derived from layered compounds by exfoliation. By a solution-based bottom-up approach using perovskite nanosheets, we have successfully fabricated multilayer nanofilms directly on SrRuO3 or Pt substrates without any interfacial dead layers. These nanofilms exhibit high dielectric constant (>200), the largest value seen so far in perovskite films with a thickness down to 10 nm. Furthermore, the superior high-κ properties are a size-effect-free characteristic with low leakage current density (<10−7 A cm−2). Our work provides ...

Journal ArticleDOI
TL;DR: In this paper, the synthesis and characterization of CsSnI3 perovskite semiconductor thin films were reported, which contained polycrystalline domains with typical size of 300 nm.
Abstract: We report on the synthesis and characterization of CsSnI3 perovskite semiconductor thin films deposited on inexpensive substrates such as glass and ceramics. These films contained polycrystalline domains with typical size of 300 nm. It is confirmed experimentally that CsSnI3 compound in its black phase is a direct band-gap semiconductor, consistent with the calculated band structure from the first principles. The band gap is determined to be ∼1.3 eV at Γ point at room temperature.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a structure with high symmetry and extraordinary electrochemical performance for Bi0.5Sr 0.5FeO3-δ, which is capable of competing effectively with the current Co-based cathode benchmark with additional advantages of lower thermal expansion and cost.
Abstract: Bi doping of SrFeO3−δ results in the formation of a structure with high symmetry and extraordinary electrochemical performance for Bi0.5Sr0.5FeO3-δ, which is capable of competing effectively with the current Co-based cathode benchmark with additional advantages of lower thermal expansion and cost.