Perovskite Structure Research Articles

Structural and Magnetic Properties of Nano Manganite La0.6Sr0.4MnO3 Obtained by Mechanochemical Synthesis Influenced by Preparation Conditions

Single phase La0.6Sr0.4MnO3 nanoparticles with perovskite structure ( R3̅C symmetry) were successfully prepared by ball milling (mechanochemical synthesis) for 1 and 10 h followed by annealing treatment at temperature 900 or 1100 °C. It was found that, the lattice parameters increase with the increase of milling time or annealing temperature. The increase of the annealing temperature results in the increase of crystallite size and the particle size. The obtained samples were found to be ferromagnetic at room temperature. The sample obtained by one hour of milling and 900 °C annealing showed high value of saturation magnetization (about 56 emu g−1) and small value of coercivity (about 31 Oe) at room temperature, while the other samples show reduced value of magnetization and higher value of coercivity. The obtained magnetic results are discussed in light of the core/shell model of nanoparticles. The effect of the presence of oxygen vacancies on the lattice parameters and magnetic properties of the obtained samples is also discussed.

Interface enhanced magnetoelectric coupling effect of multiferroic liquids based on CoFe2O4@BaTiO3 core shell particles

A new type CoFe2O4@BaTiO3 (CFO@BTO) multiferroic liquid with different CoFe2O4 (CFO) particle sizes was constructed, and its magnetic properties, electrical properties, and magnetoelectric coupling effects were systematically studied. XRD results show that the CFO phase has a spinel structure, whereas the BaTiO3 (BTO) phase has a perovskite structure, with no obvious heterophase formation. It can be seen from the SEM diagram that the CFO powder has a cuboid shape, and the CFO particle size (1.56 × 0.58 × 0.48 µm, 3.16 × 1.04 × 0.66 µm, 6.47 × 1.53 × 1.40 µm, and 11.19 × 2.64 × 2.28 µm) gradually increased with increasing calcination temperature(T = 450 ℃, 550 ℃, 650 ℃, 750 ℃). TEM results show that the composite particles have obvious core-shell structure. From the hysteresis loop, it can be seen that the saturation magnetization (Ms) of the CFO@BTO powder gradually increases with increasing CFO size. The sedimentation stability of the multiferroic liquid gradually decreases, the dielectric constant and residual polarization (Pr) decrease first and then increase, and the magnetoelectric coefficient and magnetoelectric coupling coefficient increase first and then decrease. When the particle size of the CFO is 6.47 × 1.53 × 1.40 µm, the maximum magnetoelectric coupling coefficient is 210.76 V/(cm·Oe) under an applied magnetic field of 50 Oe, which realizes a strong magnetoelectric coupling effect at room temperature.

Exploring the effects of the alkaline earth metal cations on the electronic structure, photostability and radiation hardness of lead halide perovskites

The growing interest to the application of perovskite solar cells (PSC) in aerospace requires great attention to the design of new absorber materials with enhanced photostability and radiation hardness. We addressed this challenge through the B-site engineering by partial replacing of Pb2+ in the complex halides with Ca2+, Sr2+, and Ba2+. Change in the material electronic properties suggests the incorporation of the substituent cations in the perovskite lattice. However, when the loading of alkaline earth halides is high, they tend to segregate to the film surface and grain boundaries. The modification of MAPbI3 and Cs0.12FA0.88PbI3 by replacing a 1% of Pb2+ with alkaline earth metal cations resulted in improvements in the photostability and radiation hardness under exposure to gamma rays and electrons beam. Depending on the material formulation, it was possible to mitigate the photochemical and radiation-induced Pb0 formation and the univalent cation phase segregation. The best of the designed perovskite absorbers could successfully tolerate high doses of gamma rays (5.5 MGy) and electron fluences (3 × 1016 e/cm2), thus outperforming significantly the non-modified material. These findings feature the incorporation of alkaline earth metal cations as a promising approach for the development of PSC with enhanced radiation hardness for aerospace applications.

A Comprehensive Comparison of the Structural, Ferroelectric, Energy Storage, and Photocatalytic Properties of Chemical Composition-Tailored Perovskite Ceramics

This article reports on the structural, ferroelectric, energy density, and photocatalytic properties of (Pb0.50Ba0.35Ca0.15)(Fe0.25Nb0.25Ti0.50)O3 [PBCTO] and (Pb0.50Ba0.50)(Fe0.25Nb0.25Zr0.1Ti0.40)O3 [PBZTO] ceramics synthesized by the solid synthesis route. X-ray diffraction and Raman spectra confirmed peaks corresponding to perovskite crystalline structure with tetragonal phase for both PBCTO and PBZTO ceramics. Slim ferroelectric hysteresis was observed in polarization-electric field measurements. Remnant polarization (Pr), and coercive field (Ec) values are ∼3.63 μC cm−2, ∼25.4 kV cm−1, and ∼1.39 μC cm−2 and 17.9 kV cm−1 for PBCTO and PBZTO, respectively. Energy densities were obtained from ferroelectric hysteresis loops. For PBCTO ceramics, the largest unreleased energy density is 0.72 J cm−3 @ 200 kV cm−1; for PBZTO ceramics, the largest unreleased energy density is 0.60 J cm−3 @200 kV cm−1. Photocatalytic performance was studied on methylene blue (MB) and methyl orange (MO) dyes under visible irradiation. The degradation percentage of MB dye in the presence of PBCTO and PBZTO was found to be 56% and 98% in 80 min with irradiation. The degradation percentage of MO dye in the presence of PBCTO and PBZTO at their respective wavelength was 48% and 97% in 120 min with irradiation. These bulk ceramics under study have shown interesting multifunctional properties useful for various potential applications.

Preparation and Properties of Nb5+-Doped BCZT-Based Ceramic Thick Films by Scraping Process.

A bottleneck characterized by high strain and low hysteresis has constantly existed in the design process of piezoelectric actuators. In order to solve the problem that actuator materials cannot simultaneously exhibit large strain and low hysteresis under relatively high electric fields, Nb5+-doped 0.975(Ba0.85Ca0.15)[(Zr0.1Ti0.9)0.999Nb0.001]O3-0.025(Bi0.5Na0.5)ZrO3 (BCZTNb0.001-0.025BiNZ) ceramic thick films were prepared by a film scraping process combined with a solid-state twin crystal method, and the influence of sintering temperature was studied systematically. All BCZTNb0.001-0.025BiNZ ceramic thick films sintered at different sintering temperatures have a pure perovskite structure with multiphase coexistence, dense microstructure and typical dielectric relaxation behavior. The conduction mechanism of all samples at high temperatures is dominated by oxygen vacancies confirmed by linear fitting using the Arrhenius law. As the sintering temperature elevates, the grain size increases, inducing the improvement of dielectric, ferroelectric and field-induced strain performance. The 1325 °C sintered BCZTNb0.001-0.025BiNZ ceramic thick film has the lowest hysteresis (1.34%) and relatively large unipolar strain (0.104%) at 60 kV/cm, showing relatively large strain and nearly zero strain hysteresis compared with most previously reported lead-free piezoelectric ceramics and presenting favorable application prospects in the actuator field.

On the synthesis and formability of high-entropy oxides

This paper reports on a straightforward and general solution-based synthesis method for high-entropy oxides (HEOs) of different types and compositions. The flexibility and simplicity of this method are hoped to drive development of new HEOs and study of their properties and applications. Thirteen HEOs with rock salt, fluorite, spinel, and perovskite structures were synthesized using a Pechini-type synthesis at temperatures significantly lower than those necessary in solid-state synthesis (400–900 °C). Metal nitrates, nitrites, chlorides, and even water-sensitive alkoxides were used as the metal precursors with the present method. The HEOs were characterized using powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Relaxation of cation size and charge rules and formability of HEOs are also discussed. The present results indicate that the classical criteria for material stability do not readily translate to high-entropy systems. For example, the well-known criteria for Goldschmidt and octahedral tolerance factors established for ordinary perovskites do not seem to describe formability of perovskite HEOs well. The discussed relaxation of cation size and charge rules will contribute to the understanding of HEO systems and development of new HEO phases.

Kinetics of N2O decomposition over bulk and supported LaCoO3 perovskites

For the first time, kinetic data on the decomposition of N2O over mixed oxide LaCoO3 with a perovskite structure have been obtained. Bulk LaCoO3 synthesized using microwave activation exhibited an increased intrinsic reaction rate with a 30 kJ mol–1 lower activation energy. Perovskite samples supported on ZrO2-La demonstrated lower intrinsic reaction rates due to the lower content of the LaCoO3 phase, but the activation energies were also lower by 50–80 kJ mol–1.

Copper-perovskite interfacial engineering to boost deNOx activity

By adjusting the Cu doping level and calcination temperature during synthesis of a series of noble metal-free lanthanum copper manganite perovskites LaCuxMn1-xO3, we show the importance of tuning the redox chemistry for optimum steering of the catalytic activity and N2 selectivity in the catalytic reduction of NO by CO. A prerequisite is the in situ formation of an extended copper-perovskite phase boundary. The associated improvement of redox and surface properties by Cu addition leads to an optimized balance of the reduction of the catalyst in the NO+CO reaction mixture. The creation of oxygen vacancies improves the reaction kinetics and initiates the NO dissociation. Strongly dependent on the calcination temperature, the Cu/Mn ratio, the reducing agent, as well as the reaction temperature as parameters for Cu-perovskite interfacial control, surface reduction can induce partial copper exsolution, significant perovskite reduction, agglomeration of exsolved Cu particles and eventual decomposition of the catalyst structure. We show that increasing the amount of initial copper incorporated into the perovskite structure can beneficially extend the phase boundary, but exceeding the amount of copper leads to increased sintering of the copper particles at the expense of catalyst activity, especially in repeated catalytic cycles. Increasing the calcination temperature, in addition to the initial sintering of the catalyst and shifting the reaction onset temperature to higher temperatures in the first cycle, improves the reduction resistance of the catalyst. Consequently, in order to form a higher amount of phase boundary-bound active sites, stronger reducing conditions than provided by the NO+CO reaction mixture are needed. This effect can be counterbalanced by using stronger reduction agents prior to performing subsequent catalytic cycles by inducing the exsolution process.

Key features of perovskite solar cells operando stabilization with ionic liquid choline cinnamate

The ionic liquid choline cinnamate was applied for the first time as a defect passivator in light-absorbing layers of perovskite solar cells (PSCs). It was found that bulk passivation with an addition of 0.5% ionic liquid notably enhances the photothermal stability of PSCs, while surface passivation leads to the opposite effect with the loss of device stability, due to the complex origin of the influence of choline cinnamate on the defect structure and microstructure of hybrid halide perovskites.

A series of Ba12M0.5Zr0.5Nb9O36 (M=Ni, Mg, Co, and Zn) microwave dielectric ceramics with hexagonal perovskite structure

A series of hexagonal perovskite Ba12M0.5Zr0.5Nb9O36 (M = Ni, Mg, Co, Zn) ceramics were prepared by solid-state reaction method. XRD and Rietveld refinement results showed that all ceramic samples belong to the hexagonal perovskite structure with R-3m space group. With different B-site ion substitution, variation of permittivity (εr) can be ascribed to the average ion polarizability. Ceramics with highest relative density exhibit maximum quality factor (Q×f) values. Among all samples, the optimal microwave dielectric properties of εr = 35.2, Q×f = 57,985 GHz, and τf = 26.4 ppm/°C for Ba12Mg0.5Zr0.5Nb9O36 were obtained, which indicated that Ba12Mg0.5Zr0.5Nb9O36 ceramic is a candidate material for microwave communication applications.

Synchrotron Radiation-Based In Situ GIWAXS for Metal Halide Perovskite Solution Spin-Coating Fabrication.

Solution-processable perovskite-based devices are potentially very interesting because of their relatively cheap fabrication cost but outstanding optoelectronic performance. However, the solution spin-coating process involves complicated processes, including perovskite solution droplets, nucleation of perovskite, and formation of intermediate perovskite films, resulting in complicated crystallization pathways for perovskite films under annealing. Understanding and therefore controlling the fabrication process of perovskites is difficult. Recently, synchrotron radiation-based in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) techniques, which possess the advantages of high collimation, high resolution, and high brightness, have enabled to bridge complicated perovskite structure information with device performance by revealing the real-time crystallization pathways of perovskites during the spin-coating process. Herein, the developments of synchrotron radiation-based in situ GIWAXS are discussed in the study of the crystallization process of perovskites, especially revealing the important crystallization mechanisms of state-of-the-art perovskite optoelectronic devices with high performance. At the end, several potential applications and challenges associated with in situ GIWAXS techniques for perovskite-based devices are highlighted.

Multiferroic properties of electrospun CoFe2O4–(Ba0.95Ca0.05)(Ti0.89Sn0.11)O3 nanocomposites for magnetoelectric and magnetic field sensing applications

Multiferroic CoFe2O4–Ba0.95Ca0.05Ti0.89Sn0.11O3 composite nanofibers (CFO–BCTSn NFs) were synthesized using a sol–gel electrospinning method. Scanning electron microscopy revealed the morphology of the composites, with fiber diameters ranging from 120 to 150 nm. Transmission electron microscopy confirmed the structure of the nanofibers, while X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy verified the formation of the spinel structure of CFO and the perovskite structure of BCTSn, with no additional phases detected. The magnetic properties of the CFO–BCTSn NFs were demonstrated by magnetic hysteresis loops (M-H), and piezoresponse force microscopy confirmed their piezoelectricity. Magnetoelectric coupling was evidenced by comparing the M-H hysteresis loops of electrically poled and unpoled CFO–BCTSn NFs samples. These composite nanofibers have the potential to be utilized in innovative, lead-free magnetoelectric and magnetic field sensing technologies at the nanoscale.

Investigation of samarium and neodymium co-doped BaCeO3 electrolyte for proton-conducting solid oxide fuel cells

BaCe0.8Sm0.2-xNdxO3-δ (x = 0, 0.05, 0.1, 0.15) powder was prepared using the glycine-nitrate combustion method, its crystal structure, microscopic morphology and electrochemical properties were investigated. X-ray diffraction analysis showed that the BaCe0.8Sm0.2-xNdxO3-δ powder with orthorhombic perovskite structure could be obtained after calcined at 1150 °C. Scanning electron microscopy showed that BaCe0.8Sm0.2-xNdxO3-δ sintered samples exhibited a dense structure. Electrochemical impedance tests showed that the substitution of Nd3+ improved the electrical conductivity of the BaCeO3-based electrolyte materials. The proton conductivity of BaCe0.8Sm0.15Nd0.05O3-δ samples reaches a maximum value of 0.035 S cm−1 in a wet air environment at 700 °C.

In-situ prepared co exsolution nano catalyst for efficient hydrogen generation via ammonia decomposition

Active and durable catalytic material for ammonia (NH3) decomposition reaction is attracting attentions for utilization of NH3 as an innovative hydrogen carrier. In this study, diverse single metal and alloy nano catalysts are prepared via in-situ exsolution method and their NH3 decomposition properties are evaluated. Transition metal cations (Ni, Co, Fe ions) are doped into the La0.43Ca0.37MxNyTi1-(x+y)O3-δ (LCMNT) perovskite oxide structure and exsolved on its surface as supported nano particles under reduction condition. The maximum doping level and chemical composition of exsolution catalysts are investigated to optimize their NH3 decomposition activity. The exsolution catalyst demonstrates improved NH3 decomposition characteristics compared to conventionally prepared infiltration catalysts, indicating higher conversion efficiency and H2 production rate. The exsolved nano catalysts also exhibit great thermochemical stability against catalyst agglomeration or surface nitriding. The results obtained in this study suggest the potential utilization of exsolution catalysts for on-site production of H2 through NH3 decomposition catalysis.

Bi-doped initiates the crystal structure reconfiguration of Aurivillius, boosts piezoelectric response, and achieve PMS activation and antibiotic degradation in Bi2LaNbTiO9-BiOBr heterojunctions

Piezo-photocatalysis has been widely accepted as a research strategy for environmental treatment. However, the outstanding issues of synergistic pressure response and charge transfer are still the difficulties in this area, so it is crucial to improve these points. Doping modification of piezoelectric materials is a well-established method to enhance the piezoelectric response and promote charge transfer by modulating the crystal structure. In this study, the crystal structure of Bi4Ti3O12 has been reconstructed by double doping substitution at A and B sites, which realizes the layer change of perovskite structure and the structural distortion of MO6 (M = Ti, Nb). This change in crystal symmetry effectively enhances the piezoelectric response of the material and combined with the construction of Bi2LaNbTiO9-BiOBr (BLNT-BOB) heterojunctions, the charge distribution is dramatically improved, and the charge transfer becomes easier. Under the dual effect of heterojunction and piezo-photocatalytic coupling, the catalyst exhibited excellent catalytic performance, and the degradation rate of BhB reached 97.24 % within 20 min, After PMS activation, the degradation rate reached 98.65 % in 16 min, which was higher than that of BLNT (59.13 %) and BOB (46.81 %), and the reaction kinetics were improved by 5.3-fold and 7.4-fold. It also showed good degradation efficiency in the treatment of antibiotics, and the soybean sprout culture experiment provided a strong proof of the applicability of the catalyst in multiple pollutants and biocompatibility. This work provides valuable insights for designing piezoelectric photocatalytic structures and analyzing the activation mechanism of PMS.

Enhanced luminescence performance in double perovskite CaSrLaSbO6: Mn4+ red emission phosphors for indoor plant growth via cation doping

Novel CaSrLaSbO6: Mn4+ red-emitting phosphors with double perovskite structure were successfully synthesized by the high-temperature solid-phase method. CaSrLaSbO6:Mn4+ phosphor showed a broad excitation band with different excitation peaks from 250 nm to 600 nm owing to the Mn4+-O2- charge transfer and 4A2g → (4T1g, 2T2g, and 4T2g) transitions of Mn4+ ions and exhibited intense deep-red emission at 678 nm attributed to the 2Eg → 4A2g transition of Mn4+ ions. To further enhance the performance of the phosphor, a cation doping method was adopted in this paper to synthesize CaSrLa1-xLnxSbO6: Mn4+ (Ln = Gd, Y) phosphors. The luminescence intensity of the samples was enhanced after doping with different cations, and the related mechanism was discussed. In addition, the microstructure and crystal field environment were systematically investigated. The luminescence intensity of the CaSrLa0.85Y0.15SbO6: Mn4+ phosphor was about 1.82 times higher than that of CaSrLaSbO6: Mn4+phosphor. The emission spectrum of the sample matched well with the absorption band of plant pigments. Furthermore, the plant growth LEDs and light-conversion film were prepared by using the optimized CaSrLa0.85Y0.15SbO6: Mn4+. The results indicate that the designed phosphors have great potential applications in agricultural cultivation.

Energy storage efficiency and electrocaloric performances in lead-free Ba0.87Ca0.13(Ti0.9Zr0.1)0.98(Zn1/3Nb2/3)0.02O3 ceramic

Ba0.87Ca0.13(Ti0.9Zr0.1)0.98(Zn1/3Nb2/3)0.02O3 ceramic was prepared using a solid-state reaction method. This work investigates their dielectric, ferroelectric, energy storage, and electrocaloric properties. X-ray diffraction analysis confirms a pure perovskite structure. The dielectric constant reaches a maximum of 9364 at 326 K. Enhanced total energy density, recovered energy density, and energy storage efficiency are observed between 303 K and 363 K. Artificial neural networks (ANNs) are employed for the indirect determination of large ECE and responsivity based solely on measured ferroelectric polarization (P(E,T)). This approach offers rapid and accurate predictions with minimal experimental data, significantly accelerating the characterization of novel electrocaloric materials. The maximum ECE occurs above the Curie temperature (TC) and increases with higher electric fields. The ceramic exhibits significant ECE parameters around TC with a broad electrocaloric temperature span. Various figures of merit, including relative cooling power, refrigerant capacity, and temperature-averaged entropy change, are explored under different electric fields, demonstrating the material's potential for green cooling devices. These figures improve monotonically with increasing field strength. A comprehensive analysis of the field dependence of ΔS (entropy change) confirms the second-order nature of the electric phase transition through master curve analysis. In conclusion, these lead-free ceramics exhibit promising applications in high-performance energy storage devices and solid-state refrigeration technology.

Coating Robust Layers on Ni-Rich Cathode Active Materials while Suppressing Cation Mixing for All-Solid-State Lithium-Ion Batteries.

This study focused on addressing the challenges associated with the incompatibility between sulfide solid electrolytes and Ni-rich cathode active materials (CAMs) in all-solid-state lithium-ion batteries. To resolve these issues, protective layers have been explored for Ni-rich materials. Lithium lanthanum titanate (LLTO), a perovskite-type material, is recognized for its excellent chemical stability and ionic conductivity, which render it a potential protective layer in CAMs. However, traditional methods of achieving the perovskite structure involve temperatures exceeding 700 °C, resulting in challenges such as LLTO agglomeration, secondary phase formation between LLTO and CAM, and cation mixing within the CAM. In this study, a rapid technique known as flash-light sintering (FLS) was employed to fabricate a uniform and pure perovskite protective layer without inducing cation mixing within the CAM. The LLTO-coated LiNi0.8Co0.1Mn0.1O2 (NCM811) with FLS treatment demonstrated minimal cation mixing and formed a fully covered dense layer. This resulted in a high initial capacity and effectively addressed the incompatibility issues between the sulfide electrolytes and CAM. The rapid FLS method not only streamlines the fabrication of LLTO-coated NCM811 but also provides opportunities for its broader application to materials that were previously deemed impractical because of high sintering temperatures.

Beyond Traditional Perovskites: Xenon's Influence on the Vibrational and Electronic Properties of K4Xe3O12

AbstractThe perovskite structure is one of the most fascinating configurations existing in nature, with its physical and chemical properties heavily influenced by the nature and oxidation states of cations, stoichiometry, and crystalline structure. Layered perovskite material K4Xe3O12, an interesting member of this family, possesses energetic properties that require detailed investigation. To establish the governing principles and quantify the observed behaviors, a detailed computational investigation is conducted into the electronic, vibrational, structural, and optical characteristics of K4Xe3O12, utilizing Density Functional Theory (DFT) calculations. The calculated elastic constants adhere to Born's criteria, affirming the mechanical stability of trigonal K4Xe3O12, with a bulk modulus (Bo) of ≈53.93 GPa. This low compressibility is intricately tied to its robust perovskite structure, featuring XeO6 octahedra sandwiched between XeO3 molecules. Precise determination of the valence‐conduction bandgap is crucial for understanding potential connections to the photodecomposition phenomenon. Using the Tran‐Blaha‐modified Becke‐Johnson (TB‐mB) potential alongside traditional generalized gradient approximation (GGA) approach, a bandgap of ≈1.32 eV is determined. Rapid fluctuations in optical properties also suggest a propensity for photodecomposition in the visible spectrum. The study provides critical insights into perovskite materials, especially those containing noble gas atoms, unveiling unique chemical and physical properties that open up new avenues for versatile applications across various fields.

Investigation of physical properties of Ba2NdX(X=Nb, Ta)O6 double perovskites for renewable energy applications

Alkali metals at the A site, coupled with rare earth transition metals featuring partly filled 4f and d orbitals at B and B’ sites in A2BB’O6 structure of double perovskites, induce complex d-f electron interactions. Present study explores the rare earth-based double perovskites Ba2NdNbO6 and Ba2NdTaO6, investigating their structural, optoelectronic, magnetic, and thermoelectric characteristics using first principles method. Computational analyses confirm the stable cubic symmetry and ferromagnetic ground state of both compounds. Negative formation enthalpies underline their thermodynamic stability. Spin polarized electronic band structures reveal direct–indirect degeneracy near the Fermi level, dominated by Nd-4f electrons. Optical investigations indicate absorption onset edges at 4.0 eV and significant absorbance peaks in the 6–10 eV range. Furthermore, the investigation into thermoelectric figure of merit reveals capability of Ba2NdNbO6 and Ba2NdTaO6 to efficiently convert heat energy in thermoelectric devices. These findings provide information for potential applications of investigated compounds in thermoelectric (TE) and optoelectronic devices; e.g., in optical absorbers, TE coolers and generators, and photonic devices.