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The crystal structure and transport properties of GeBi2Te4 are investigated as a layered compound with potential applications as thermoelectric materials. A disordered arrangement of Ge and Bi atoms in a septuple‐layer structure is discovered through synchrotron radiation X‐ray diffraction and transmission electron microscopy. Neutron pair distribution function analysis revealed the presence of discordant Ge atoms with an off‐centering distance of 0.12 Å at 300 K. The thermal conductivity of GeBi2Te4 is very low due to the strong phonon scattering. This is a result of the three Einstein local oscillators coupled with the disordered arrangement of atoms. This study also explores further the structural characteristics of these materials and their associated phonon scattering processes. The effect of Sb substitution for Ge on the electrical transport properties of the sample is profound, resulting in a change from p‐type to n‐type conduction. An enhanced thermoelectric figure of merit (ZT) of 0.45 at 523 K in the in‐plane direction is obtained. This research provides valuable insights into the crystal structure and transport properties of GeBi2Te4, showcasing its promising role as a thermoelectric material with potential for near‐room‐temperature applications. [ABSTRACT FROM AUTHOR]

Calcium carbonate (CaCO3), the most abundant biogenic mineral on earth, plays a crucial role in various fields such as hydrosphere, biosphere, and climate regulation. Of the four polymorphs, calcite, aragonite, vaterite, and amorphous CaCO3, vaterite is the most enigmatic one due to an ongoing debate regarding its structure that has persisted for nearly a century. In this work, based on systematic transmission electron microscopy characterizations, crystallographic analysis and machine learning aided molecular dynamics simulations with ab initio accuracy, we reveal that vaterite can be regarded as a polytypic structure. The basic phase has a monoclinic lattice possessing pseudohexagonal symmetry. Direct imaging and atomic-scale simulations provide evidence that a single grain of vaterite can contain three orientation variants. Additionally, we find that vaterite undergoes a second-order phase transition with a critical point of ~190 K. These atomic scale insights provide a comprehensive understanding of the structure of vaterite and offer advanced perspectives on the biomineralization process of calcium carbonate. The structure of vaterite has been debated for a century. Combining systematic TEM characterisations, crystallographic analysis, and machine learning aided molecular dynamics simulations, the authors unlock the structural mystery in vaterite. [ABSTRACT FROM AUTHOR]

Nanoparticles with high-index facets are intriguing because such facets can lend the structure useful functionality, including enhanced catalytic performance and wide-ranging optical tunability. Ligand-free solid-state syntheses of high index-facet nanoparticles, through an alloying-dealloying process with foreign volatile metals, are attractive owing to their materials generality and high yields. However, the role of foreign atoms in stabilizing the high-index facets and the dynamic nature of the transformation including the coarsening and facet regulation process are still poorly understood. Herein, the transformation of Pt salts to spherical seeds and then to tetrahexahedra, is studied in situ via gas-cell transmission electron microscopy. The dynamic behaviors of the alloying and dealloying process, which involves the coarsening of nanoparticles and consequent facet regulation stage are captured in the real time with a nanoscale spatial resolution. Based on additional direct evidence obtained using atom probe tomography and density functional theory calculations, the underlying mechanisms of the alloying-dealloying process are uncovered, which will facilitate broader explorations of high-index facet nanoparticle synthesis. Faceted nanoparticles with high-index planes exposed usually bear promising material functionalities. Here, the authors directly observe the coarsening and facet regulation process of tetrahexahedra Pt nanoparticles by using in-situ gas-phase TEM. [ABSTRACT FROM AUTHOR]

Knowledge of deformation mechanisms in aragonite, one of the three crystalline polymorphs of CaCO3, is essential to understand the overall excellent mechanical performance of nacres. Dislocation slip and deformation twinning were claimed previously as plasticity carriers in aragonite, but crystallographic features of dislocations and twins have been poorly understood. Here, utilizing various transmission electron microscopy techniques, we reveal the atomic structures of twins, partial dislocations, and associated stacking faults. Combining a topological model and density functional theory calculations, we identify complete twin elements, characters of twinning disconnection, and the corresponding twin shear angle (~8.8°) and rationalize unique partial dislocations as well. Additionally, we reveal an unreported potential energy dissipation mode within aragonite, namely, the formation of nanograins via the pile-up of partial dislocations. Based on the microstructural comparisons of biogenic and abiotic aragonite, we find that the crystallographic features of twins are the same. However, the twin density is much lower in abiotic aragonite due to the vastly different crystallization conditions, which in turn are likely due to the absence of organics, high temperature and pressure differences, the variation in inorganic impurities, or a combination thereof. Our findings enrich the knowledge of intrinsic crystal defects that accommodate plastic deformation in aragonite and provide insights into designing bioengineering materials with better strength and toughness. [ABSTRACT FROM AUTHOR]

Curvature presents a powerful approach to design atomic structure and tailor material properties in atomically thin transition metal dichalcogenides (TMDs). The emerging TMD core-shell architecture, in which a multilayer TMD shell encapsulates a curved nanoparticle core, presents the opportunity to controllably induce defects into a TMD crystal by strategically constructing the shape of the underlying core. However, harnessing this potential platform first requires robust characterization of the unique structural features present in the core-shell architecture. To this end, transmission electron microscopy (TEM) and scanning TEM (STEM) are particularly powerful tools for direct structural characterization of 2D materials with a high spatial resolution and precision. Here, we reveal and describe defects inherently present in the TMD core-shell architecture. We develop a comprehensive framework to classify the observed defects and discuss potential origins and implications of structural variations. We utilize high resolution S/TEM to reveal the relationship between defects and their associated strain fields. Furthermore, we demonstrate that TMD shells often possess a wide range of interlayer spacings with varied spatial distribution. By exploring the rich array of structural defects inherently present in the TMD core-shell architecture, we provide an important foundation to ultimately induce exotic properties in TMDs through sophisticated defect engineering. [ABSTRACT FROM AUTHOR]

Spinel-structured LiMn2O4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmission electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn3+ at the LMO electrode surface, promoting an oxidation state change to Mn4+, which suppresses dissolution. [ABSTRACT FROM AUTHOR]

The incorporation of nanostructured carbon has been recently reported as an effective approach to improve the cycling stability when Si is used as high-capacity anodes for the next generation Li-ion battery. However, the mechanism of such notable improvement remains unclear. Herein, we report in-situ transmission electron microscopy (TEM) studies to directly observe the dynamic electrochemical lithiation/delithiation processes of crumpled graphene-encapsulated Si nanoparticles to understand their physical and chemical transformations. Unexpectedly, in the first lithiation process, crystalline Si nanoparticles undergo an isotropic to anisotropic transition, which is not observed in pure crystalline and amorphous Si nanoparticles. Such a surprising phenomenon arises from the uniformly distributed localized voltage around the Si nanoparticles due to the highly conductive graphene sheets. It is observed that the intimate contact between graphene and Si is maintained during volume expansion/contraction. Electrochemical sintering process where small Si nanoparticles react and merge together to form large agglomerates following spikes in localized electric current is another problem for batteries. In-situ TEM shows that graphene sheets help maintain the capacity even in the course of electrochemical sintering. Such in-situ TEM observations provide valuable phenomenological insights into electrochemical phenomena, which may help optimize the configuration for further improved performance [ABSTRACT FROM AUTHOR]

With about two-thirds of all used energy being lost as waste heat, there is a compelling need for high-performance thermoelectric materials that can directly and reversibly convert heat to electrical energy. However, the practical realization of thermoelectric materials is limited by their hitherto low figure of merit, ZT, which governs the Carnot efficiency according to the second law of thermodynamics. The recent successful strategy of nanostructuring to reduce thermal conductivity has achieved record-high ZT values in the range 1.5-1.8 at 750-900 kelvin, but still falls short of the generally desired threshold value of 2. Nanostructures in bulk thermoelectrics allow effective phonon scattering of a significant portion of the phonon spectrum, but phonons with long mean free paths remain largely unaffected. Here we show that heat-carrying phonons with long mean free paths can be scattered by controlling and fine-tuning the mesoscale architecture of nanostructured thermoelectric materials. Thus, by considering sources of scattering on all relevant length scales in a hierarchical fashion-from atomic-scale lattice disorder and nanoscale endotaxial precipitates to mesoscale grain boundaries-we achieve the maximum reduction in lattice thermal conductivity and a large enhancement in the thermoelectric performance of PbTe. By taking such a panoscopic approach to the scattering of heat-carrying phonons across integrated length scales, we go beyond nanostructuring and demonstrate a ZT value of ?2.2 at 915 kelvin in p-type PbTe endotaxially nanostructured with SrTe at a concentration of 4 mole per cent and mesostructured with powder processing and spark plasma sintering. This increase in ZT beyond the threshold of 2 highlights the role of, and need for, multiscale hierarchical architecture in controlling phonon scattering in bulk thermoelectrics, and offers a realistic prospect of the recovery of a significant portion of waste heat. [ABSTRACT FROM AUTHOR]

Thermoelectric materials can directly generate electrical power from waste heat but the challenge is in designing efficient, stable and inexpensive systems. Nanostructuring in bulk materials dramatically reduces the thermal conductivity but simultaneously increases the charge carrier scattering, which has a detrimental effect on the carrier mobility. We have experimentally achieved concurrent phonon blocking and charge transmitting via the endotaxial placement of nanocrystals in a thermoelectric material host. Endotaxially arranged SrTe nanocrystals at concentrations as low as 2% were incorporated in a PbTe matrix doped with Na2Te. This effectively inhibits the heat flow in the system but does not affect the hole mobility, allowing a large power factor to be achieved. The crystallographic alignment of SrTe and PbTe lattices decouples phonon and electron transport and this allows the system to reach a thermoelectric figure of merit of 1.7 at ~800 K. [ABSTRACT FROM AUTHOR]

The defect and interfacial structure in a Fe3O4/BaTiO3 heteroepitaxial bilayer was investigated by scanning transmission electron microscopy. The results show that the Fe3O4 film grew epitaxially on BaTiO3. The orientation relationship between Fe3O4, BaTiO3 and MgO is [100]Fe3O4//[100]BaTi3O//[100]MgO and (010)Fe3O4//(010)BaTiO3//(010)MgO. An initial interfacial nucleation layer was formed that partially accommodated the lattice mismatch strain between BaTiO3 and MgO. This investigation indicates that the formation of this buffer layer provides a high-quality BaTiO3 surface for subsequent Fe3O4 growth, resulting in a semicoherent interface. The Fe3O4 surface is nearly atomically abrupt (roughness Rrms - 0.78 nm). The Fe3O4 film exhibits magnetic domains with a diameter in the range of 0.4-2 μm. [ABSTRACT FROM AUTHOR]

Abstract: Ni x Co1− x O/ZrO2(CaO) directionally solidified eutectic composites have been previously shown to form Ni(Co) metallic interphases mediating Ni x Co1− x O and ZrO2(CaO) phases upon chemical reduction of the composite at high temperatures. Vickers and nanoindentation experiments indicate characteristics of toughening enhancement in the reduced composite due to plastic deformation of the confined metallic interphase. This paper reports on the effect of size scale and chemistry of the metallic interphase on the phenomenological aspects of deformation behavior and the extent of plasticity at different length scales in the reduced eutectic model system. Transmission electron microscopy observations clearly show that a size-dependent deformation mechanism operates within the metallic interphase. A decrease in the extent of strain energy absorption, dislocation activity and twinning propensity is observed within the ductile interphase with decreasing size scale. In addition, a transition is observed in the small-scale deformation mechanism of the metallic interphase with changes in the composition of the interphase. [Copyright &y& Elsevier]

We report a study of the nanoscale mass-density fluctuations of heterogeneous optical dielectric media, including nanomaterials and biological cells, by quantifying their nanoscale light-localization properties. Transmission electron microscope images of the media are used to construct corresponding effective disordered optical lattices. Light-localization properties are studied by the statistical analysis of the inverse participation ratio (IPR) of the localized eigenfunctions of these optical lattices at the nanoscale. We validated IPR analysis using nanomaterials as models of disordered systems fabricated from dielectric nanoparticles. As an example, we then applied such analysis to distinguish between cells with different degrees of aggressive malignancy. [ABSTRACT FROM AUTHOR]

This letter reports a facile approach for morphologic control of complex oxide nanostructures patterned by “soft” electron beam lithography (soft-eBL). The authors demonstrate fabrication of epitaxial nanofrustum and nanopyramidal morphologies of ferroelectric BaTiO3 and magnetic CoFe2O4 lines, with controlled zig-zag or smooth edges. The dimensional and shape control is achieved by simply tuning the patterning parameters such as resist thickness and patterning directions with respect to underlying substrate orientation. The crystal orientation, element distribution, and piezoelectric behavior of BaTiO3 nanofrustums are evaluated with analytical transmission electron microscopy and piezoresponse force microscopy. It is argued that soft-eBL allows for exquisite control over morphology, shape evolution, and orientation of zero- and one-dimensional nanostructures akin to what has been possible in the past with semiconductor heterostructures by thin film approaches. [ABSTRACT FROM AUTHOR]

The authors report fabrication of multiferroic BiFeO3 (BFO) by the soft electron beam lithography technique. BiFeO3 nanopatterns with less than 100 nm characteristic dimension are fabricated from its liquid-phase precursor on diverse substrates. The chemical constituents and phase purity are characterized by transmission electron microscopy. The ferroelectric behavior is confirmed by piezoresponse force microscopy. A saturation magnetization of about 10 emu/cm3 is observed, demonstrating the multiferroic characteristic of the BFO nanopatterns. Furthermore, the BFO nanolines pattened on SrTiO3 substrate exhibit a bamboolike structure, which can serve as an excellent model system for investigating the contribution of grain boundaries to the leakage current. [ABSTRACT FROM AUTHOR]

NixCo1-xO/ZrO2(CaO) directionally solidified eutectics (DSEs) form a ductile metallic interphase after they are chemically reduced at high temperatures. Vickers indentation tests have previously shown a significant change in the crack propagation behavior of the reduced composites due to plastic deformation and strain energy absorption mechanisms operating in the system after reduction. This paper focuses on structural and chemical characterization of NixCo1-xO/ZrO2, (CaO) DSEs after reduction. Analytical transmission electron microscopy techniques such as energy dispersive x-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS) show elimination of oxygen and formation of nanoscale Ni(Co) solid. [ABSTRACT FROM AUTHOR]

Knowledge of deformation mechanisms in aragonite, one of the three crystalline polymorphs of CaCO3, is essential to understand the overall excellent mechanical performance of nacres. Dislocation slip and deformation twinning were claimed previously as plasticity carriers in aragonite, but crystallographic features of dislocations and twins have been poorly understood. Here, utilizing various transmission electron microscopy techniques, we reveal the atomic structures of twins, partial dislocations, and associated stacking faults. Combining a topological model and density functional theory calculations, we identify complete twin elements, characters of twinning disconnection, and the corresponding twin shear angle (~8.8°) and rationalize unique partial dislocations as well. Additionally, we reveal an unreported potential energy dissipation mode within aragonite, namely, the formation of nanograins via the pile-up of partial dislocations. Based on the microstructural comparisons of biogenic and abiotic aragonite, we find that the crystallographic features of twins are the same. However, the twin density is much lower in abiotic aragonite due to the vastly different crystallization conditions, which in turn are likely due to the absence of organics, high temperature and pressure differences, the variation in inorganic impurities, or a combination thereof. Our findings enrich the knowledge of intrinsic crystal defects that accommodate plastic deformation in aragonite and provide insights into designing bioengineering materials with better strength and toughness. [ABSTRACT FROM AUTHOR]

[Display omitted] Inspired by the unique architectures composed of hard and soft materials in natural and biological systems, synthetic hybrid structures and associated hard-soft interfaces have recently evoked significant interest. Soft matter is typically dominated by structural fluctuations even at room temperature, while hard matter is governed by rigid mechanical behavior. This dichotomy offers considerable opportunities to leverage the disparate properties offered by these components across a wide spectrum spanning from basic science to engineering insights with significant technological overtones. Such hybrid structures, which include polymer nanocomposites, DNA functionalized nanoparticle superlattices, and metal organic frameworks to name a few, have delivered promising insights into the technologically relevant applications such as catalysis, environmental remediation, optoelectronics, and medicine. The interfacial structure between the hard and soft phases demonstrates features across a variety of length scales and often strongly influence the functionality of hybrid systems. While scanning/transmission electron microscopy (S/TEM) has proven to be a valuable tool for acquiring intricate molecular and nanoscale details of these interfaces, the unusual nature of hybrid composites presents a suite of challenges that make assessing or establishing structure–property relationships especially difficult. There are additional considerations at all stages of sample analysis from preparing electron-transparent samples to obtaining sufficient contrast to resolve the interface between dissimilar materials given the dose sensitivity of soft materials. We discuss each of these challenges and supplement a review of recent developments in the field with additional experimental investigations and simulations to present solutions for attaining a nano or molecular-level understanding of these interfaces. These solutions present a host of opportunities for investigating the role interfaces play in this unique class of functional materials. [ABSTRACT FROM AUTHOR]

The article discusses the study of revealing nanoscale mineralization pathways of hydroxyapatite using in situ liquid cell transmission electron microscopy. Topics discussed include treat impairments in hard tissues or overcome pathological calcification in soft tissues, a detailed understanding of mineralization pathways of calcium phosphate materials is needed; and report a detailed mechanistic study of hydroxyapatite (HA) mineralization pathways in an artificial saliva solution.

We report a new quasi-one-dimensional compound KMn[sub 6]Bi[sub 5] composed of parallel nanowires crystallizing in a monoclinic space group C2/m with a = 22.994(2) Å, b = 4.6128(3) Å, c = 13.3830(13) Å and β = 124.578(6)°. The nanowires are infinite [Mn6Bi5]- columns each of which is composed of a nanotube of Bi atoms acting as the cladding with a nanorod of Mn atoms located in the central axis of the nanotubes. The nanorods of Mn atoms inside the Bi cladding are stabilized by Mn-Mn bonding and are defined by distorted Mn-centered cluster icosahedra of Mn13 sharing their vertices along the b axis. The [Mn6Bi5]- nanowires are linked with Weak internanowire Bi-Bi bonds and charge balanced with K+ ions. The [Mn6Bi5]- nanowires were directly imaged by high-resolution transmission electron microscopy and scanning transmission electron microscopy. Magnetic susceptibility studies show one-dimensional characteristics with an antiferromagnetic transition at ~75 K and a small average effective magnetic moment (1.56 µB/Mn for H || b and 1.37 µB/Mn for H ⊥ b) of Mn from Curie-Weiss fits above 150 K. Specific heat measurements reveal an electronic specific heat coefficient γ of 6.5(2) mJ K-2(mol-Mn)-1 and a small magnetic entropy change ΔSmag ≈ 1.6 J K-1 (mol-Mn)-1 across the antiferromagnetic transition. In contrast to a metallic resistivity along the column, the resistivity perpendicular to the column shows a change from a semiconducting behavior at high temperatures to a metallic one at low temperatures, indicating an incoherent-to-coherent crossover of the intercolumn tunneling of electrons. [ABSTRACT FROM AUTHOR]

The crystallization kinetics of Zn0.3In1.4Sn0.3O3 (ZITO-30) thin films is investigated via isothermal in situ transmission electron microscopy measurements. Extensive analysis is conducted to reveal the nucleation mechanism and growth rate at four different temperatures. The results show that the nucleation rate in this system is time-dependent and continuously decelerates following a power law decay. The crystal growth rate is constant at a given temperature, and interface-limited growth is the controlling mechanism in the kinetics of amorphous ZITO-30 crystallization. The activation energy for the overall process and interface growth are derived from the experimental data. A morphological study of the grains shows that the {100} interfaces have low mobility and are responsible for the anisotropic crystal shapes. It is found that the {111} and {100} planes of the crystal form parallel to the film-vapor interface during the nucleation process. The results demonstrate a rather complex yet tractable correlation between the experimental results and theoretical underpinning in complex multicomponent oxide thin films. [ABSTRACT FROM AUTHOR]

We examine the thermodynamics of phase separation and ordering in the ternary CaxPb1-xS and SrxPb1-xS systems by density-functional theory combined with a cluster expansion and Monte Carlo simulations. Similar to most other ternary III-V or IV-VI semiconductor alloys, we find that bulk phase separation is thermodynamically preferred for PbS-CaS. However, we predict the surprising existence of stable, ordered ternary compounds in the PbS-SrS system. These phases are previously unreported ordered rocksalt-based compounds: SrPb3S4, SrPbS2, and Sr3PbS4. The stability of these predicted ordered phases is confirmed by transmission electron microscopy observations and band gap measurements. We believe this work paves the way for a combined theory-experiment approach to decipher complex phase relations in multicomponent chalcogenide systems. [ABSTRACT FROM AUTHOR]

We explored the effect of Cd substitution on the thermoelectric properties of PbTe in an effort to test a theoretical hypothesis that Cd atoms on Pb sites of the rock salt lattice can increase the Seebeck coefficient via the formation of a resonance level in the density of states near the Fermi energy. We find that the solubility of Cd is less than previously reported, and CdTe precipitation occurs to create nanostructuring, which strongly suppresses the lattice thermal conductivity. We present detailed characterization including structural and spectroscopic data, transmission electron microscopy, and thermoelectric transport properties of samples of PbTe-x% CdTe-0.055% Pbl2 (x = 1,3, 5, 7, 10), PbTe-1% CdTe-y% Pbl2 (y = 0.03, 0.045, 0.055, 0.08, 0.1,0.2), PbTe-5% CdTe-y% Pbl2 (y = 0.01,0.03, 0.055, 0.08), and PbTe-1% CdTe-z% Sb (z = 0.3, 0.5, 1, 1.5, 2, 3, 4, 5, 6). All samples follow the Pisarenko relationship, and no enhancement of the Seebeck coefficient was observed that could be attributed to a resonance level or a distortion in the density of states. A maximum ZT of ~1.2 at ~720 K was achieved for the PbTe-1% CdTe-0.055% Pbl2 sample arising from a high power factor of ~17 µW/(cm K²) and a very low lattice thermal conductivity of ~0.5 W/(m K) at ~720 K. [ABSTRACT FROM AUTHOR]

Abstract: The composition and microstructure of five thermoelectric materials, PbTe, SnTe, NaPb0.65Sn0.35Te and NaPb18-xSnxBiTe20 (x = 5, 9), were investigated by advanced transmission electron microcopy. We confirm that the pure PbTe, SnTe, and NaPb0.65Sn0.35BiTe have a uniform crystalline structure and homogeneous compositions without any nanoscale inclusions. On the other hand, the nominal NaPb9Sn9BiTe20 phase contains extensive inhomogeneities and nanostructures with size distribution of 3-7 nm. We find that the chemical architecture of the NaPb13Sn5BiTe20 member of the series to be more complex; besides nanoscale precipitates, self-organized lamellar structures are present which were identified as PbTe and SnTe by composition analysis and transmission electron microscopy image simulations. Density functional theory calculations suggest that the arrangement of the lamellar structures conforms to the lowest total energy configuration. Geometric-phase analyses revealed large distributed elastic strain around the nanoscale inclusions and lamellar structures. We propose that interface-induced elastic perturbations in the matrix play a decisive role in affecting the phonon-propagation pathways. The interfaces further enhance phonon scattering which, in turn, reduces the lattice thermal conductivity in these systems that directly results directly in improvement in the thermoelectric figure of merit. [ABSTRACT FROM AUTHOR]

Abstract: Pristine and Pd-doped nanoporous SnO x thin films were fabricated via a sol–gel route. The Pd-doped film exhibited enhanced H2 gas-sensing performance, in terms of higher sensitivity and shorter response time. Structural characterization was performed to investigate the effect of Pd doping on the microstructure evolution of the films. The grain and pore size of Pd-doped film, as measured using transmission electron microscopy and grazing-incidence small-angle X-ray scattering (GISAXS), are both smaller than those of undoped film. In particular, the pore size evolution of the films during annealing was quantitatively monitored in situ using synchrotron-based GISAXS. Knudsen gas diffusion and depletion layer models were employed to evaluate the microstructure influence on the gas sensitivity semi-quantitatively. The results suggest that the microstructure of the Pd-doped film is critical for improving the gas sensitivity but cannot account for the total sensitivity enhancement, implying other mechanisms could play a more important role. [Copyright &y& Elsevier]

The existence of new ordered rocksalt-based compounds SrPb3S4, SrPbS2, and Sr3PbS4 in the title system is predicted by DFT calculations, and experimentally confirmed by TEM and band gap measurements. [ABSTRACT FROM AUTHOR]