Cu-Atom Locations in Rocksalt SnTe Thermoelectric Alloy.

The development of functional thermoelectric materials requires direct evidence of dopants' locations to rationally design the electronic and phononic structure of the host matrix. In this study, Cs-corrected scanning transmission electron microscopy and energy dispersive X-ray spectroscopy is employed at the atomic scale to identify Cu atoms' locations in a Cu-doped SnTe thermoelectric alloy. It is revealed that Cu atoms in the rocksalt SnTe form solid solutions at both Sn and Te sites, contrary to their electronegativity order and the intentional Cu doping at Sn sites.

Atomic-Scale Behavior of Perovskite-Supported Ir-Pd-Ru Nanoparticles under Redox Atmospheres.

An advanced materials solution utilizing the concept of "smart catalysts" could be a game changer for today's automotive emission control technology, enabling the efficient use of precious metals via their two-way switching between metallic nanoparticle forms and ionic states in the host perovskite lattice as a result of the cyclical oxidizing/reducing atmospheres. However, direct evidence for such processes remains scarce; therefore, the underlying mechanism has been an unsettled debate. Here, we use advanced scanning transmission electron microscopy to reveal the atomic-scale behaviors for a LaFePdO-supported Ir-Pd-Ru nanocatalyst under fluctuating redox conditions, thereby proving the reversible dissolution/exsolution for Ir and Ru but with a limited occurrence for Pd.

Understanding Micro and Atomic Structures of Secondary Phases in Cu-Doped SnTe.

Highly efficient thermoelectric materials require, including point defects within the host matrix, secondary phases generating positive effects on lowering lattice thermal conductivity (κ ). Amongst effective dopants for a functional thermoelectric material, SnTe, Cu doping realizes the ultra-low κ approaching the SnTe amorphous limit. Such effective κ reduction is first attributed to strong phonon scattering by substitutional Cu atoms at Sn sites and interstitial defects in the host SnTe.

Singular behaviour of atomic ordering in Pt-Co nanocubes starting from core-shell configurations.

The ordered structure of platinum-cobalt (Pt-Co) alloy nanoparticles has been studied actively because the structure influences their magnetic and catalytic properties. On the Pt-Co alloy's surface, Pt atoms preferentially segregate during annealing to reduce the surface energy. Such surface segregation has been shown to promote the formation of an ordered structure near the surface of Pt-Co thin films.

Quantitative Characterization of the Thermally Driven Alloying State in Ternary Ir-Pd-Ru Nanoparticles.

Compositional and structural arrangements of constituent elements, especially those at the surface and near-surface layers, are known to greatly influence the catalytic performance of alloyed nanoparticles (NPs). Although much research effort often focuses on the ability to tailor these important aspects in the design stage, their stability under realistic operating conditions remains a major technical challenge. Here, the compositional stability and associated structural evolution of a ternary iridium-palladium-ruthenium (Ir-Pd-Ru) nanoalloy at elevated temperatures have been studied using interrupted scanning transmission electron microscopy and theoretical modeling.

Subpercent Local Strains Due to the Shapes of Gold Nanorods Revealed by Data-Driven Analysis.

Analysis of subpercent local strain is important for a deeper understanding of nanomaterials, whose properties often depend on the strain. Conventional strain analysis has been performed by measuring interatomic distances from scanning transmission electron microscopy (STEM) images. However, measuring subpercent strain remains a challenge because the peak positions in STEM images do not precisely correspond to the real atomic positions due to disturbing influences, such as random noise and image distortion.

Highly Stable and Active Solid-Solution-Alloy Three-Way Catalyst by Utilizing Configurational-Entropy Effect.

Since 1970, people have been making every endeavor to reduce toxic emissions from automobiles. After the development of a three-way catalyst (TWC) that concurrently converts three harmful gases, carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NO ), Rh became an essential element in automobile technology because only Rh works efficiently for catalytic NO reduction. However, due to the sharp price spike in 2007, numerous efforts have been made to replace Rh in TWCs.

- Observation of the Continuous Phase Transition in Determining the High Thermoelectric Performance of Polycrystalline SnSe.

We report a comprehensive - phase-change study on polycrystalline SnSe via high-temperature X-ray diffraction and - high-voltage transmission electron microscopy from room temperature to 843 K. The results clearly demonstrate a continuous phase transition from to starting from 573 to 843 K, rather than a sudden transition at 800 K. We also find that the thermal-conductivity rise at high temperature after the phase transition, as commonly seen in pristine SnSe, does not occur in SnSe, leading to a high thermoelectric figure of merit.

Imaging the Polymorphic Transformation in a Single Cu₆Sn₅ Grain in a Solder Joint.

In-situ observations of the polymorphic transformation in a single targeted Cu₆Sn₅ grain constrained between Sn-0.7 wt % Cu solder and Cu-Cu₃Sn phases and the associated structural evolution during a solid-state thermal cycle were achieved via a high-voltage transmission electron microscope (HV-TEM) technique. Here, we show that the monoclinic η'-Cu₆Sn₅ superlattice reflections appear in the hexagonal η-Cu₆Sn₅ diffraction pattern upon cooling to isothermal 140 °C from 210 °C.