In‐grain dislocation‐induced lattice strain fluctuations are recently revealed as an effective avenue for minimizing the lattice thermal conductivity. This effect could be integratable with electronic enhancements such as by band convergence, for a great advancement in thermoelectric performance. This motivates the current work to focus on the thermoelectric enhancements of p‐type PbTe alloys, where monotelluride‐alloying and Na‐doping are used for a simultaneous manipulation on both dislocation and band structures. As confirmed by synchrotron X‐ray diffractions and Raman measurements, the resultant dense in‐grain dislocations induce lattice strain fluctuations for broadening the phonon dispersion, leading to an exceptionally low lattice thermal conductivity of ≈0. 4 W m‐K−1. Band structure calculations reveal the convergence of valence bands due to monotelluride‐alloying. Eventually, the integration of both electronic and thermal improvements lead to a realization of an extraordinary figure of merit zT of ≈2.5 in Na0.03Eu0.03Cd0.03Pb0.91Te alloy at 850 K.

Lone-pair electrons (LPEs) ns2 in subvalent 14 and 15 groups lead to highly anharmonic lattice and strong distortion polarization, which are responsible for the groups’ outstanding thermoelectric and optoelectronic properties. However, their dynamic stereochemical role in structural and physical properties is still unclear. Here, by introducing pressure to tune the behavior of LPEs, we systematically investigate the lone-pair stereochemical role in a Bi2O2S. The gradually suppressed LPEs during compression show a nonlinear repulsive electrostatic force, resulting in two anisotropic structural transitions. An orthorhombic-to-tetragonal phase transition happens at 6.4 GPa, caused by the dynamic cation centering. This structural transformation effectively modulates the optoelectronic properties. Further compression beyond 13.2 GPa induces a 2D-to-3D structural transition due to the disappearance of the Bi-6s2 LPEs. Therefore, the pressure-induced LPE reconfiguration dominates these anomalous variations of lattice, electronic, and optical properties. Our findings provide new insights into the materials optimization by regulating the characters of LPEs.

The strengthening of polycrystalline metals based on grain refinement has previously been reported to be no longer effective below a critical grain size of approximately 10-15 nm (Refs. 1, 2). That report imposed a limit on grain size tuning for synthesizing stronger materials. Here, we report our study using a diamond-anvil cell coupled with radial X-ray diffraction to track in situ the yield stress and deformation texturing of pure nickel samples with various average grain sizes. Continuous strengthening isobserved from 200 nm to the minimum grain size of 3 nm. Strengthening as a function of grain size is enhanced in the lower grain size regime below 20 nm. We achieved an ultra-high strength of ~ 4.2 gigapascals in nickel, 10 times larger than the values for commercial nickel material. The maximum flow stress of 10.2 gigapascals is reached in 3 nm nickel in the pressure range of this study. Plasticity simulation and transmission electron microscopy (TEM) examination reveal that the high strength observed in 3 nm nickel is caused by the superposition of strengthening mechanisms: partial and full dislocation hardening plus grain boundary plasticity suppression. These results rejuvenate the search for ultra-strong metals via materials engineering.Understanding the strengthening of nanograined metals has been puzzling, as both mixed results of size softening and hardening have been reported [3][4][5][6] . The main challenges in resolving this debate are the difficulty in synthesizing high quality, ultrafine metal samples for traditional tension or hardness tests and making statistically reproducible measurements. Some researchers have pointed out that reported size softening may be related to materials preparation 7 . Porosity, amorphous regions and impurities may be introduced during sample preparation methods like inert gas condensation and electrodeposition, leading to softening in

However, in most cases, stoichiometricamounts peroxides like H 2 O 2 and tertbutyl hydroperoxide (TBHP) were used as exogenous oxidizing reagents and oxygen sources, [2] resulting in massive waste and an increase in costs. [3] The strategy that water serves as the oxygen source to produce high-value organic chemicals has drawn more attention due to its low price and cleanliness, [4] yet its inertia under ambient temperatures leads to more energy consumption in practical working conditions. Electrochemical methods with waste-free electrons as redox agents provide a green and mild pathway to watermediated oxidation of organics, [5] where the balance between the oxidation of organics and the competitive oxygen evolution reaction (OER) is deemed as the main problem. [6] Inspired by the tandem catalysis tactic, turning this competition between the OER and the selective oxidation of styrene to benzaldehyde into cooperation should be feasible, but it has rarely been achieved.Single-atom catalysts (SACs) meet with great favor in electro catalysis for their superior activity, higher metal-utilization efficiency, and enhanced selectivity. [7] In the past decade, enormous encouraging SACs have been created and utilized to catalyze the oxygen reduction reaction, the OER, and other heterogeneous reactions. [8] However, the activity of SACs often suffers the limit for complex reactions with multiple intermediates, because the single site is not able to catalyze efficiently all the reactions in the whole system. [9] Although introducing extra active centers into SACs has the potential to break this limit, [10] spatiotemporal transfer of intermediates over catalytic sites and inherent synergetic mechanisms remain unexplored, thus leading to a low product yield and undesirable side reactions. Besides, insufficient cognition on the reconstruction of the catalytic sites in working conditions also increases the difficulty of their design. Therefore, constructing active sites with a specific function to catalyze complex reactions in a tandem system still confronts a great challenge.Herein, we fabricate a single-atom catalyst with Cr atoms atomically dispersed at CoSe 2 support (Cr 1 /CoSe 2 ), in which Co and Cr sites are endowed with a specific function to oxidize water and styrene respectively. Especially, the anchored Cr single atoms could not only serve as the active sites for the Electrocatalytic oxidation of organics using water as the oxygen source is a prospective but challenging method to produce high-value-added chemicals; especially, the competitive oxygen evolution reaction (OER) limits its efficiency. Herein, a tandem catalysis strategy based on a single-atom catalyst with Cr atoms atomically dispersed at a CoSe 2 support (Cr 1 /CoSe 2 ) is presented. Thereinto, Co and Cr sites are endowed with a specific function to activate water and styrene respectively, and the competition between the OER and styrene oxidation is turned into mutual benefits via cooperated active sites. Under a potential of 1.6 V Ag/AgCl , exce...

Medium‐entropy (Ti,Zr,Hf)C ceramics were prepared by hot pressing a dual‐phase medium‐entropy carbide powder with low oxygen content (0.45 wt%). The results demonstrate that the medium‐entropy (Ti,Zr,Hf)C ceramics sintered at 2100°C had a relative density of 99.2% and an average grain size of 1.9 ± 0.6 μm. The flexural strength of (Ti,Zr,Hf)C carbide ceramics at room temperature was 579 ± 62 MPa. With an increase in temperature to 1600°C, the flexural strength showed an increase up to 619 ± 57 MPa, and had no significant degradation even up to 1800°C. The high‐temperature flexural strengths of (Ti,Zr,Hf)C were obviously higher than those of the monocarbide ceramics (TiC, ZrC, and HfC). The primary strengthening mechanism in (Ti,Zr,Hf)C could be attributed to the high lattice parameter mismatch effects between TiC and ZrC, which not only inhibited the fast grain coarsening of (Ti,Zr,Hf)C ceramics, but also increased the grain‐boundary strength of the obtained ceramics.