Perovskite-type Materials Research Articles

Thermal decomposition, phase formation and microstructure analysis of surfactant assisted sol-gel derived La0.6Sr0.4CoO3-δ material

A single-phase of perovskite-type oxide material can be prepared at a processing temperature relatively lower than 1000 °C through a sol-gel method. However, it is affected by the nature of chemical additives employed during the synthesis process. In the present work, sol-gel derived lanthanum strontium cobaltite, La0.6Sr0.4CoO3-δ (LSC64) material is prepared using various non-ionic surfactants namely polyoxyethylene (10) oleyl ether (Brij-97), polyoxyethylene octyl phenyl ether (Triton-X-100) and polyoxyethylene (20) sorbitan monooleate (Tween-80). The prepared powders of the LSC material is subsequently subjected to the thermal decomposition, phase formation and microstructure analysis by a thermal gravimetric analyzer, an X-ray diffractometer and a scanning electron microscope (SEM), respectively. The as-synthesized powders are calcined at different temperatures based on the thermal gravimetric analysis results. X-ray diffractometer results reveal that all of the calcined powders consist of more than 90 % perovskite phase of LSC64 and other secondary phases such as cobalt oxide, lanthanum oxide and strontium carbonate. The Brij-97-based and Tween-80-based calcined powders have morphology of typical clump-like network structure, while the Triton-X-100-based calcined powder has morphology of flake-like network structure.

Nano-manipulation of Bi0.7Sr1.3Co0.5Fe1.5O6−δ double perovskite oxide for oxygen separation: assessment on morphology structure and oxygen desorption properties

A novel double perovskite oxide-type Bi0.7Sr1.3Co0.5Fe1.5O6−δ (BiSCF-D) is nano- manipulated and evaluated. X-ray diffraction results reveal that perovskite-type BiSCF-D materials exhibit typical cubic shape with Pm-3m space group. The BiSCF-D was synthesised by solid-state reaction method and further nanosized with milling treatment. Nanosizing was carried out by ball mill with ball to powder ratio at 10:1, 15:1, and 20:1 wt% for 5 h, assigned as B5 10:1, B5 15:1, and B5 20:1, respectively. The structure and oxygen desorption of prepared powders were investigated. The crystal structure and particle size were determined by using Rietveld refinement and particle size analyser. The thermogravimetry-differential thermal analysis and oxygen temperature programmed desorption measurement are applied to find out oxygen desorption ability. The results showed that B5 15:1 has the lowest impurity and smallest particle size among the prepared powders. It was found that B5 15:1 has better oxygen desorption properties compared with other treatments with sufficiently desorption characteristics.

Effect of Metal Content on Ethanol Decomposition over Ni-Co Catalysts Supported on La-Ce Oxides.

The search for catalysts with features that can improve coke resistance and decrease byproduct formation is a current goal in H2 production from renewable sources. In this work, the effect of the presence of Ni nanoparticles over Co/La-Ce oxides on the ethanol decomposition reaction was studied. Catalysts were synthetized using as precursor a La0.8Ce0.2NixCo1-xO3 perovskite-type material to ensure a low segregation of phases and a high dispersion of metals. After reduction at 873 K, the perovskite structure was destroyed, and metal Co-Ni particles were supported over a lanthanum-cerium oxide. The materials were characterized by different techniques before and after reaction. Solids exhibited metal particle sizes between 5 and 15 nm demonstrating the advantages of the preparation method to obtain Ni-Co alloys. Although the results of adsorption of ethanol followed by diffuse reflectance infrared fourier transformed spectroscopy (DRIFTS) showed acetate species strongly adsorbed on the catalyst’s surface, the material (Ni0.7Co0.3/La0.8Ce0.2) with the lowest particle size was the most stable system leading to the lowest amount of carbon deposits during ethanol decomposition. This catalyst showed the better performance, with a higher ethanol conversion (98.4%) and hydrogen selectivity (75%). All catalysts exhibited carbonaceous deposits, which were an ordered and disordered carbon phase mixture.

Descriptors for dielectric constants of perovskite-type oxides by materials informatics with first-principles density functional theory

ABSTRACT Dielectric materials that can realize downsizing and higher performance in electric devices are in demand. Perovskite-type materials of the form ABO3 are potential candidates. However, because of the numerous conceivable compositions of perovskite-type oxides, finding the best composition is technically difficult. To obtain a reasonable guideline for material design, we aim to clarify the relationship between the dielectric constants and other physical and chemical properties of perovskite-type oxides using first-principles density functional theory (DFT) and partial least-squares regression analysis. The more important factors affecting the dielectric constants are predicted based on variable importance in projection (VIP) scores. The dielectric constant strongly correlates with the ionicity of the B cations and the density of states of the conduction bands of the B cations.

Coexistence of parabolic and linear band crossings and electron-doped spin-gapless properties in rhombohedral type YbBO3

Very recently, a novel Dirac half-metal has been investigated in the perovskite-type lanthanum manganite (LaMnO3) by Ma et al. [1] and the half metallicity with 100% spin polarization is discovered. More remarkably, multiple linear Dirac crossings are observed around the Fermi energy level in the spin-up direction. Inspired by this work, another perovskite-type material YbBO3, which has been synthesized before, is investigated by first principles calculation. Results confirm the presence of half metallicity in this material with also multiple Dirac-like linear and parabolic band crossings around the Fermi level. The estimated Curie temperature is 469.4 K and the mechanic and dynamic stabilities have been verified. Besides, the elastic anisotropy is revealed with the directional dependent Young’s modulus and shear modulus, together with the acoustic wave properties. The effect of the uniform strain, electron doping and spin-orbital coupling on the electronic structures have been also accessed. In particular, nearly spin-gapless semiconducting behavior with linear or parabolic energy dispersions is obtained by electron doping. Moreover, several thermodynamic properties have been examined under temperature from 0 to 500 K and pressure from 0 to 5 GPa. In combination, we expect YbBO3 can attract more research attention and even facilitate the spintronic application.

Mesoporous LaFeO3 perovskite derived from MOF gel for all-solid-state symmetric supercapacitors

Sol-gel strategies have attracted enormous attention in synthesis of perovskite-type oxides due to their excellent chemical homogeneity and possibility in controlling the size, morphology, chemical properties and texture of particles. Nevertheless, their complicated, time-consuming process and weak control over porous structure impeded their potential use in preparation of energy storage materials. Herein, a simple and rapid strategy based on MOF gel (MIL-100-Fe) is developed for fabricating mesoporous perovskite-type materials. The MOF gel can be synthesized in controllable time duration without multi complexing agent, particular pH conditions and high temperature treatment. The synthesized perovskite LaFeO3 has mesoporous structure and the pore size is concentrated at 2 nm, which contribute to a specific capacitance of 241.3 F g−1 at 1 A g−1 with retention of 68% even at a high current density of 20 A g−1. Meanwhile, the all-solid-state symmetric supercapacitor shows a wide potential window of 1.8 V, and an outstanding energy density of 34 W h kg−1 at a power density of 900 W kg−1 with 92.2% capacitance retention after 5000 cycles, outperforming previously reported perovskite-type electrode materials and even comparable to MOF derived iron oxides. Thus, this study opens a new way to construct porous perovskite-type electrode materials for supercapacitors, which can combine the chemical homogeneity of sol-gel technology and the porous properties of MOF template together.

Tin based organic-inorganic hybrid semiconductors with reversible phase transition and dielectric anomaly.

Organic-inorganic hybrid materials with perovskite structure have recently attracted tremendous interest due to their structural tunability and rich functional properties, such as phase transition and photoelectric properties. Within this context, two discrete tin-based organic-inorganic hybrid compounds [(FMBA)2SnCl6] (1) and [(FMBA)2SnBr6] (2) were prepared by the reaction of 3-fluoro-N-methylbenzylamine (FMBA) with SnX4 (X = Cl, Br) in the corresponding concentrated halogen acids HX. Differential scanning calorimetry (DSC) and dielectric measurements showed that both compounds underwent reversible phase transition and dielectric anomaly at a phase transition point above 400 K. Crystal structure analyses revealed that the phase transition mainly originated from the order and disorder of a fluorine-substituted organic amine structure at low and high temperatures. Meanwhile, both compounds showed a semiconducting property with optical bandgaps of 4.24 eV for 1 and 2.58 eV for 2. This finding of two Sn(iv)-based metal halides with prominent phase transition and semiconducting behaviors will expand an executable pathway for designing multifunctional perovskite-type switchable materials.

Development of a PrBaMn2O5+δ-La0.8Sr0.2Ga0.85Mg0.15O3-δ composite electrode by scaffold infiltration for reversible solid oxide fuel cell applications

In this study, a PrBaMn2O5+δ (PBMO)-La0.8Sr0.2Ga0.85Mg0.15O3-δ (LSGM) composite catalyst was developed for use in a reversible solid oxide fuel cell (SOFC) electrode. Through a chemical compatibility test, a heat treatment temperature at which secondary phases did not form between LSGM and PBMO was determined, and a PBMO-LSGM composite electrode material was synthesized by a scaffold infiltration technique capable of synthesizing a catalyst within the appropriate temperature range. A half-cell test consisting of two identical PBMO-LSGM composite electrodes supported on LSGM pellets found that the optimum infiltration amount of PBMO with respect to the LSGM scaffold was approximately 20 wt%. Electrochemical performance measurements under reversible SOFC operating conditions on a half-cell with 19.7 wt% PBMO-LSGM composite electrodes showed a specific resistance and activation energy significantly lower than those of conventional Ni-based cermet and perovskite-type materials, indicating that the developed PBMO-LSGM composite electrode is a promising electrocatalyst for reversible SOFCs.

Energy Conversion Processes with Perovskite-type Materials.

Mixed oxides derived from the perovskite structure by combination of A- and B-site elements and by partial substitution of oxygen provide an immense playground of physico-chemical properties. Here, we give an account of our own research conducted at the Paul Scherrer Institute on perovskite-type oxides and oxynitrides used in electrochemical, photo(electro)chemical and catalytic processes aimed at facing energy relevant issues.

Fabrication of Stannate Perovskite Structure as Optoelectronics Material: An Overview

This paper presents a review of recent fabrication progress of perovskite-type material suited for the future optoelectronics applications. Wide varieties of optoelectronic devices include solar cell, liquid displays, transparent FETs, etc are becoming the mainstream for the future electronics global industry. In June 2015, the major breakthrough of perovskite structure in solar energy harvesting with PCE of 20.1% has achieved. Since then, numerous research has been conducted progressively to further enhance the performance of the perovskite structure as new alternative materials for optoelectronics applications. The perovskite-type oxide is having typical ABO3 crystallized structure. It is one of an important class of materials that have many exceptional physical properties such as superconductivity, colossal magnetoresistance, ferromagnetic, piezoelectric, high-transition-temperature superconductivity, ferroelectricity, piezoelectricity, and photoelectrochemical sensitivity. In this paper, we reviewed development progress one of the major classes of perovskite-type materials namely Stannate-based. Calculated data from simulation results such as DFT and first principle were excluded and only fabricated devices are covered in this paper.

Perovskite Structured Nanomaterials: An Advanced Key for Global Development of Nanotechnology

Starting with a history of the fundamental science, currently, the perovskite structures exemplify the extensive manifestation of crystal chemistry which is associated with the smart synthesis techniques to develop a new type of material. The perovskite structures exhibit the most efficient single accomplished ceramic host. Perovskite structured nanomaterials had originated from CaTiO3. They are made up by the assembling of distinct materialistic components and follow the general configuration ABX3. Perovskite type metal oxide nanomaterial shows a wide range of ferroelectric, piezoelectric, and pyroelectric properties along with numerous optoelectrical effects. They get the facility to the various advanced technical applications due to the excellency in their properties. The photocatalytic activity may be one of the plausible and impulsive applications of that very special type of materials. Most elements in the periodic table are able to take part in designing the perovskite-type materials. Perovskite structured nanoparticles (NPs) are applying rapidly for global development because of their higher responsiveness and degree of function, large surface area, size-dependent properties etc and unfold the new possibilities in the field of nanotechnology.

Sol-gel synthesis, crystalline phase, optical absorption, and photo-luminescence behavior of cerium-doped (Ba0.5Sr0.5)FeO3−δ powders

The cerium- and iron-based perovskite type materials have received attention due to their applications in solid oxide fuel cells, sensors, catalysts, and gas separation membranes. An attempt has been made here to synthesize (Ba0.5Sr0.5)(Fe1−xCex)O3−δ (x = 0–1.0) compounds and characterize them for crystalline phases, photoluminescence and optical absorption properties. They are shown to exhibit phases as perovskite-type cubic for x = 0, cubic as well as orthorhombic in the composition range 0.1 ≤ x ≤ 0.6 and orthorhombic alone for 0.8 ≤ x ≤ 1.0. The lattice parameter of cubic phase increases with cerium content, value being ∼3.937 Å and 3.981 Å for x = 0 and 0.60, respectively with Z = 1 and space group Pm3m. The orthorhombic cell has ao = 8.871 Å, bo = 6.392 Å, co = 5.991 Å, Z = 4 and space group Pnma for the composition x = 1.0. Cerium insertion leads to lattice expansion, weakening of metal-oxygen bonds, creation of oxygen vacancies, M4+ → M3+ (M = Ce and/or Fe) conversion, and creation of defect levels within the band gap. Their photoluminescence spectra provide evidence for structural defects including oxygen vacancies. The optical absorption peaks at 620 and 700 nm are attributed to various charge transfer transitions. The characteristics make the (Ba0.5Sr0.5)(Fe1−xCex)O3−δ system technological viable for oxygen separation from air.

Frontispiece: (CH3NH3)AuX4⋅H2O (X=Cl, Br) and (CH3NH3)AuCl4: Low‐Band Gap Lead‐Free Layered Gold Halide Perovskite Materials

Three low-band gap lead-free layered gold halide perovskite-type materials have been prepared using solution methods. All three compounds exhibit exotic perovskite-related structures that have not been previously reported in the literature. The replacement of toxic Pb with Au results in measured band gaps lower than 2.5 eV accompanied with a weak blue emission due to the electronic transition between Au-6s and Au-5d. For more detail see the Full Paper by B. Saparov et al. on page 9875 ff.

Mott insulator behavior in the yttrium-based antimoniate oxide Ba2YSbO6

A careful experimental and theoretical study of the double perovskite type material Ba2YSbO6 is reported. The results show that this yttrium-based antimoniate oxide crystallizes in a cubic structure, Fm3¯m (#225) space group, with evidence of the cationic ordering that characterizes a rocksalt superstructure, and tolerance factor slightly less than the unit (τ = 0.9791) due to the size differences between the Y-O6 and Sb-O6 octahedrons. The magnetic response shows weak ferromagnetic effects for the temperature values studied (50, 200 and 300 K), with evidence of an antiferromagnetic reentrance at T = 118 K under the application of low magnetic fields, which is attributed to the presence of polar ordering, accompanied by octahedral distortions caused by the movement of the cations Y3+ and Sb5+, whose effects are no longer observed in the presence of a fairly high external magnetic field (of the Tesla order). The results of the optical characterization by diffuse reflectance suggest the occurrence of a band gap Eg = 4.61 eV, which is characteristic of an insulating material. The electronic structure calculations corroborate the insulating nature of the Ba2YSBO6 complex perovskite. The results allow classifying this material as a Mott insulator, in which the occurrence of intra-site spin-exchange facilitates unpaired spins to the 4d-t2g Yttrium states, mediated by the 2p Oxygen orbitals and 5p Antimony orbitals, resulting in the ferromagnetic character of the insulating material.

Research progress of perovskite materials as catalysts

Perovskite-type materials have become a research hotspot in the field of materials science due to their excellent structural stability and physicochemical properties. This paper briefly reviews the preparation methods of perovskite materials and their use as catalysts.

Thermochemical stability of Fe- and co-functionalized perovskite-type SrTiO3 oxygen transport membrane materials in syngas conditions

The materials typically used for oxygen transport membranes, Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) tend to decompose due to their low thermochemical stability under reducing atmosphere. Fe- and Co-doped SrTiO3 (SrTi1-x-yCoxFeyO3-δ, x + y ≤ 0.35) (STCF) materials showing an oxygen transport comparable to LSCF have great potential for application in ion-transport-devices. In this study, the thermochemical stability of pure perovskite-structured STCF was investigated after annealing in a syngas atmosphere at 600–900 °C. The phase composition of the materials after annealing was characterized by means of X-ray diffraction (XRD). The thermodynamic activities of SrO, FeO, and CoO in the STCF materials were evaluated using Knudsen effusion mass spectrometry (KEMS). Co-doped SrTiO3 (STC) materials were not stable after annealing in the syngas atmosphere above 5 mol% Co-substitution. Ruddlesden-Popper-like phases and SrCO3 were detected after annealing at 600 °C. In contrast, Fe substitution (STF) showed good stability after annealing in syngas upto 35 mol% substitution.

In-situ hydrogenation of furfural conversion to furfuryl alcohol via aqueous-phase reforming of methanol

It is a promising pathway to reduce the dependence on fossil fuels and obtain the bio-fuels or chemicals production from biomass derivatives. The conversion from furfural (FFR) to furfuryl alcohol (FFA) is an important industrial technology using the liquid-phase hydrogenation method with external hydrogen gas. However, the natural environment is threatened by the security of external hydrogen gas, toxicant catalyst, and the high energy consumption. Recently, in-situ hydrogenation is a novel method to converse FFR to FFA at mild reaction conditions to replace the dangerous external hydrogen gas. In this paper, we reported an efficient in-situ hydrogenation method via aqueous-phase reforming of methanol using Pt loading MgTiO3 (perovskite-type material) at mild conditions. Pt nanoparticles were high dispersion on the nano-MgTiO3-450 surface, and CH3OH and H2O were reformed to produce hydrogen gas on the catalyst surface through the action of Pt nanoparticles. A part of active hydrogen could be involved in the reduction of Pt2+ to Pt0, resulting in the perfect recyclability of the Pt@MT-450 catalyst. The other part of active hydrogen were participated in the hydrogenation of FFR conversion to FFA under the interaction of Pt and Mg elements. The in-situ hydrogenation of FFR to FFA using Pt@MT-450 is an effectively pathway to reduce the reaction conditions than that with external hydrogen gas.

Analysis of solid-state reaction in the performance of doped calcium manganites for thermal storage

Solid-state reaction is a potentially cost-effective route to obtain perovskite-type materials suitable for thermochemical energy storage (TCES). This work analyses the influence of the synthesis conditions on a doped calcium manganite, CaCr0.1Mn0.9O3-δ, since it has been identified as a promising material for TCES. The macrostructure shows noticeable dependence with mixing time of precursors. The perovskite, with general chemical formula ABO3, possesses secondary phases for all the synthesis conditions explored, as confirmed by X-ray diffraction analysis. The dopant effect of chromium on the crystallographic lattice is studied by the Rietvel refinement method from the comparison with CaMnO3-δ compound structure. Customized non-isothermal and isothermal experiments are performed via thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). From these experiments, an oxidation temperature of around 900 °C; energy storage density higher than 150 J/g; reaction reversibility and stable cycling performance are obtained, facts that reflect a high potential for application in concentrating solar power plants.

CaTiO3 Perovskite in the Photocatalysis of Textile Wastewater

Perovskite-type CaTiO3 material was synthesized by the polymeric precursor method and characterized. The powder was applied as a promising alternative to TiO2 photocatalyst. Photocatalytic reaction parameters were optimized by surface analysis methodology on the degradation of methylene blue under UV radiation. After optimization, complex textile- and tannery wastewaters were treated and the COD reduction was evaluated. At optimized conditions (pH=11.2 and 1 g L-1 of catalyst concentration), the results obtained for the photodegradation of the real wastewater after 240 min of irradiation were 45% COD reduction for both effluents. The reactions were adjusted to the pseudo first order kinetic and the rate constants were 2.07 x 10-3 (min-1) and 2.23 x 10- 3 (min-1) for COD reduction for textile- and tannery wastewaters, respectively.

Dual Oxygen Defects in Layered La1.2Sr0.8-xBaxInO4+δ (x = 0.2, 0.3) Oxide-Ion Conductors: A Neutron Diffraction Study.

The title compounds exhibit a K2NiF4-type layered perovskite structure; they are based on the La1.2Sr0.8InO4+δ oxide, which was found to exhibit excellent features as fast oxide-ion conductor via an interstitial oxygen mechanism. These new Ba-containing materials were designed to present a more open framework to enhance oxygen conduction. The citrate-nitrate soft-chemistry technique was used to synthesize such structural perovskite-type materials, followed by annealing in air at moderate temperatures (1150 °C). The subtleties of their crystal structures were investigated from neutron powder diffraction (NPD) data. They crystallize in the orthorhombic Pbca space group. Interstitial O3 oxygen atoms were identified by difference Fourier maps in the NaCl layer of the K2NiF4 structure. At variance with the parent compound, conspicuous oxygen vacancies were found at the O2-type oxygen atoms for x = 0.2, corresponding to the axial positions of the InO6 octahedra. The short O2–O3 distances and the absence of steric impediments suggest a dual oxygen-interstitial mechanism for oxide-ion conduction in these materials. Conductivity measurements show that the activation energy values are comparable to those typical of ionic conductors working by simple vacancy mechanisms (~1 eV). The increment of the total conductivity for x = 0.2 can be due to the mixed mechanism driving both oxygen vacancies and interstitials, which is original for these potential electrolytes for solid-oxide fuel cells.