We report a facile synthetic protocol to prepare mesoporous FeS2 without the aid of hard template as an electrocatalyst for hydrogen evolution reaction (HER). The materials with high surface area were successfully prepared by sol–gel method following sulfurization treatment in H2S atmosphere. A remarkable HER catalytic performance was achieved low overpotential 96 mV at current density 10 mA·cm–2 and Tafel slope 78 per decade under alkaline conditions (pH 13). theoretical calculations...

We develop phase diagrams for single-domain epitaxial barium strontium titanate films on cubic substrates as a function of the misfit strain based Landau–Devonshire phenomenological model similar to one developed by Pertsev et al. [Phys. Rev. Lett. 80, 1988 (1998)]. The biaxial epitaxy-induced internal stresses enable transformations unusual ferroelectric phases that are not possible in single crystals and bulk ceramics. dielectric response is calculated taking into account formation...

A series of heteroepitaxial Ba0.6Sr0.4TiO3 were grown on 0.29(LaAlO3):0.35(Sr2TaAlO6) substrates using pulsed-laser deposition. X-ray characterization revealed compressive in-plane stresses in the thinnest films, which relaxed a continuous fashion with increasing thickness. theoretical treatment misfit strain was good agreement measured out-of-plane lattice parameter. The low-frequency dielectric constant to be significantly less than bulk value and found decrease rapidly for films 100 nm....

Monodomain contributions to the electrocaloric effect in mechanically free (bulk) and laterally clamped (thin film) BaTiO3 are computed using a thermodynamic analysis. The authors show that intrinsic coefficient at electric fields sufficient destroy discontinuous ferroelectric phase transition results an adiabatic temperature change of 8K agrees closely with giant value 12K recently observed experimentally for lead zirconate titanate thin films [A. S. Mischenko et al., Science 311, 1270...

A thermodynamic analysis of the electrocaloric (EC) effect in BaTiO3 ferroelectric thin films has been carried out under differing mechanical boundary conditions. It is shown that both magnitude and temperature at which it maximized depend not only on extent applied field change but also value initial field. For fields smaller than a critical EC largest phase transition strong function temperature. external electrical larger this value, conversely, higher weak Perfect lateral clamping...

A thermodynamic analysis has been carried out to investigate the role of dislocations in ferroelectric materials. Due coupling stress field dislocation and polarization, there is a drastic variation polarization near dislocation. These gradients result strong depolarizing fields that suppress region extends over several nanometrers. In epitaxial films, these should formation dead layers severely degrade properties. The detrimental effect such regions will be enhanced ultrathin thin hence...

There has been significant progress on the fundamental science and technological applications of complex oxides multiferroics. Among oxide thin films, barium strontium titanate (BST) become material choice for room-temperature-based voltage-tunable dielectric due to its large tunability low microwave loss at room temperature. BST film varactor technology based reconfigurable radio frequency (RF)/microwave components have demonstrated with potential lower size, weight, power needs a future...

Abstract Herein we introduce an environmentally friendly approach to the synthesis of symmetrical and asymmetrical aromatic azo compounds by using air as sole oxidant under mild reaction conditions in presence cost‐effective reusable mesoporous manganese oxide materials.

The electrolysis of water provides a powerful pathway for the storage and conversion clean renewable energy. Therefore, development earth-abundant, inexpensive, highly efficient electrocatalysts contributes great deal to overall efficiency electrolytic system. Here, inspired by low charge transfer resistance mixed-valence cations, favorable H atom binding energy cobalt, high electrical conductivity graphene, we report facile synthesis strategy synthesize spinel ternary oxide material...

The MnO(100) facets with higher adsorption energy of O species can largely promote the electrocatalytic activity.

A map showing regions of stability possible domain structures and relative fractions domains in a polytwin structure is developed for epitaxial heterostructures with active layers which undergo cubic–tetragonal or tetragonal–orthorhombic transformation. This map, also applicable to film–substrate systems, shows the dependence on misfit strain, lattice parameters product phase, mechanical stress. uniaxial stress field applied during cooling down from growth temperature strongly affects...

A thermodynamic model is presented that describes the polarization and dielectric response of ferroelectric-paraelectric bilayers multilayers. It shown a strong electrostatic coupling between layers results in suppression ferroelectricity at critical paraelectric layer thickness. The bilayer expected to have gigantic similar anomaly near Curie–Weiss temperature homogeneous ferroelectrics this numerical analysis carried out for pseudomorphic (001) BaTiO3∕SrTiO3 heteroepitaxial on SrTiO3...

We have studied the effect of misfit strain on microstructure and properties ferroelectric lead zirconate titanate thin films. changed by varying film thickness domain formation epitaxial PbZr0.2Ti0.8O3 (PZT) films grown pulsed laser deposition (001) LaAlO3 substrates with La0.5Sr0.5CoO3 (LSCO) electrodes. The nominal PZT was varied from 60 to 400 nm LSCO electrode kept constant at 50 nm. X-ray diffraction experiments show that relax via a domains, fraction which increase thickness. c-axis...

Voltage-modulated scanning force microscopy (Piezoresponse microscopy) is applied to investigate the domain structure in epitaxial PbZr0.2Ti0.8O3 ferroelectric thin films grown on (001) SrTiO3. By monitoring vertical and lateral differential signals from photodetector of atomic microscope it possible separate out observe out-of-plane in-plane polarization vectors film individually. The relative orientation across a 90° wall observed. Nucleation new reversed 180° domains at studied its impact...

The tunability of epitaxial barium strontium titanate films is analyzed theoretically using a phenomenological model. relative dielectric constant Ba0.5Sr0.5TiO3 (BST 50/50) as function the applied external electric field calculated and an field–misfit strain phase diagram developed to assist in interpretation behavior. On basis these results, BST 50/50 misfit provided compared with experimental data literature. Analysis shows that high can be achieved by adjusting especially vicinity...

We present a quantitative study of the thickness dependence polarization and piezoelectric properties in epitaxial (001) PbZr0.52Ti0.48O3 films grown on SrRuO3-buffered SrTiO3 substrates. High-resolution transmission electron microscopy reveals that even thinnest (∼8nm) are fully relaxed with dislocation density close to 1012cm−2 spacing approximately 12 nm. Quantitative ferroelectric measurements show drastic degradation out-of-plane constant (d33) switched (ΔP) as function decreasing...

A generalized Landau-Ginzburg model is constructed and used to develop a methodology for analyzing graded ferroic materials. Material system inhomogeneities are assumed arise from compositional, temperature, or stress gradients. These spatial nonuniformities shown give rise local order parameters having corresponding variation. Functionally systems thus found result in nonuniform free energies with attendant internal potentials, the latter of which evidenced by displacements materials's...

Compositionally layered BaxSr1−xTiO3 (Ba0.60Sr0.40TiO3–Ba0.75Sr0.25TiO3–Ba0.90Sr0.10TiO3) 220nm thin film heterostructures were fabricated on Pt coated high resistivity Si substrates via the metal organic solution deposition technique (MOSD). Optimization of material design was achieved by evaluating two integration schemes, namely, single- and multianneal process protocols. Materials characterization demonstrated that both protocols resulted in smooth, dense, crack-free films with a single...

Structural transformations and the relative variation in band gap energy (ΔEg) of (0001) gallium nitride (GaN) films as a function equibiaxial in-plane strains are studied by density functional theory. For relatively small compressive misfits (−6%–0%), is estimated to be around its strain-free value, while for tensile (0%–6%), it decreases approximately 45%. In addition, at large (>14.5%), our calculations indicate that GaN may undergo structural phase transition from wurtzite...

Abstract Titanium alloys find extensive use in the aerospace and biomedical industries due to a unique combination of strength, density, corrosion resistance. Decades mostly experimental research has led large body knowledge processing-microstructure-properties linkages. But much existing understanding point defects that play significant role mechanical properties titanium is based on semi-empirical rules. In this work, we present results detailed self-consistent first-principles study was...

Methylammonium lead iodide (CH3NH3PbI3, MAPbI3) belongs to the group of organic–inorganic halide perovskites (OIHPs) that exhibit exceptional electrical and optical behavior suitable for photovoltaic applications. However, improving its structural chemical stability robustness remains a challenge OIHPs be considered feasible active material in optoelectronic devices. This is due fact this very susceptible degrade under various intrinsic extrinsic factors. Therefore, it crucial understand...

A series of heteroepitaxial BaxSr1−xTiO3 thin films with composition x=0.50 were deposited on (001) MgO substrates by pulsed-laser deposition. The thickness the was varied from 14 to 500 nm produce a systematically decreasing level in-plane tensile stresses. microstructural and crystallographic features determined via transmission electron microscopy x-ray diffraction. theoretical treatment misfit strain as function film is in agreement measured out-of-plane lattice parameters. Electrical...