trical conductivity, S is Seebeck coefficient, T is the absolute temperature, and κ is the thermal conductivity (κ = electronic (κ e) + lattice thermal conductivity (κ L)). [2,3] The state-of-the-art bismuth telluride-based thermoelectric (TE) materials have been used for refrigeration applications. [4] However, their ZT is limited to about 1 at room temperature, making such cooling devices less powerful and cost-competitive than other conventional technologies such as mechanical vapor-compression cooling systems. Further improving the ZT would facilitate their widespread application in industrial waste heat harvesting and electronic device cooling. [5] Maximizing ZT requires the enhancement of the power factor (PF = S 2 σ) and the reduction of thermal conductivity. [6,7] Several approaches have recently been implemented to enhance ZT, including improvement of PF by optimizing carrier concentration, [8-10] band convergence, [11,12] resonant levels, [13] energy barrier filtering, [14] and reducing κ L by alloying, [15] all-scale hierarchical architectures [16-18] and nanostructuring. [19-21] In particular, reduction of κ L by nanostructuring or through formation of nanocomposites has been demonstrated to be an effective Based on the Seebeck and Peltier effects, state-of-the-art bismuth telluridebased thermoelectric materials, which are capable of direct and reversible conversion of thermal to electrical energy, have great potential in energy harvesting and solid-state refrigerators. However, their widespread use is limited by their low conversion efficiency, which is determined by the dimensionless figure-of-merit (ZT). Significant enhancement of ZT is a great challenge owing to the common interdependence of electrical and thermal conductivity. Here, it is demonstrated that by incorporating nanoamorphous boron into the p-type Bi 0.5 Sb 1.5 Te 3 , a record high ZT of 1.6 at 375 K is achieved. It is shown that a high density of nanostructures and dislocations due to the incorporation of the boron inclusions, leads to a significant reduction of thermal conductivity and improved charge transport. The findings represent an important step to further promote the development of thermoelectric technology and its widespread application in solid-state refrigeration and power generation from waste heat.

Strengthening of magnesium (Mg) is known to occur through dislocation accumulation, grain refinement, deformation twinning, and texture control or dislocation pinning by solute atoms or nano-sized precipitates. These modes generate yield strengths comparable to other engineering alloys such as certain grades of aluminum but below that of high-strength aluminum and titanium alloys and steels. Here, we report a spinodal strengthened ultralightweight Mg alloy with specific yield strengths surpassing almost every other engineering alloy. We provide compelling morphological, chemical, structural, and thermodynamic evidence for the spinodal decomposition and show that the lattice mismatch at the diffuse transition region between the spinodal zones and matrix is the dominating factor for enhancing yield strength in this class of alloy.

The development of xenon plasma focused ion-beam (Xe + PFIB) milling technique enables sitespecific sample preparation with milling rates several times larger than the conventional gallium focused ion-beam (Ga + FIB) technique. As such, the effect of higher beam currents and the heavier ions utilized in the Xe + PFIB system is of particular importance when investigating material properties. To investigate potential artifacts resulting from these new parameters, a comparative study is performed on transmission electron microscopy (TEM) samples prepared via Xe + PFIB and Ga + FIB systems. Utilizing samples prepared with each system, the mechanical properties of CrMnFeCoNi high-entropy alloy (HEA) samples are evaluated with in situ tensile straining TEM studies. The results show that HEA samples prepared by Xe + PFIB present better ductility but lower strength than those prepared by Ga + FIB. This is due to the small ion-irradiated volumes and the insignificant alloying effect brought by Xe irradiation. Overall, these results demonstrate that Xe + PFIB systems allow for a more efficient material removal rate while imparting less damage to HEAs than conventional Ga + FIB systems. The rapid development of micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS), which utilize materials at the micron scale and below, has resulted in a growing number of potential applications in electronic devices 1. Mechanical properties are of particular importance for applications in M/NEMS as efforts seek to improve the functionality and reliability of advanced electronic devices. Continuing efforts have focused on understanding how the mechanical properties of these materials change with decreasing dimensions 2-6. To facilitate this understanding, in situ straining transmission electron microscopy (TEM) is commonly used to test the mechanical properties 7-10 and observe deformation mechanisms 11-17 of small-sized samples. In situ straining TEM allows for simultaneous structural characterisation and mechanical property testing 13,15,18 , providing opportunities for building direct relationships between microstructure, deformation mechanisms, and mechanical properties of small-sized materials. Sample preparation is of particular importance when studying small-sized materials in the TEM 19. Traditionally, these TEM samples are prepared using a focused ion-beam (FIB) with a gallium ion (Ga +) source to thin samples from bulk to ~100 nm 20-26. Despite technological advances, the material removal rates of Ga + FIB systems have remained too low for researchers hoping to increase sample preparation efficiency 27. To help facilitate more efficient sample preparation, researchers have developed FIB systems with alternative ion sources such as the Xe + plasma FIB (Xe + PFIB) 27. As an alternative to Ga + ions, Xe + PFIB systems utilize inert Xe gas as the milling media resulting in material removal rates around six times larger than for Ga + mills 27 , which enables the preparation of samples with larger dimensions. On...

In article number 2000757, Xiaolin Wang and co‐workers make a breakthrough in the performance of ultra‐high thermoelectrics in p‐type bulk BiSbTe/Boron nanocomposite materials, which has great potential for wide application in solid‐state refrigeration and power generation.

Plastic deformation in ceramic materials is normally only observed in nanometre-sized samples. However, we have observed high levels of plasticity (>50% plastic strain) and excellent elasticity (6% elastic strain) in perovskite oxide Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3, under compression along <100>pc pillars up to 2.1 μm in diameter. The extent of this deformation is much higher than has previously been reported for ceramic materials, and the sample size at which plasticity is observed is almost an order of magnitude larger. Bending tests also revealed over 8% flexural strain. Plastic deformation occurred by slip along {110} <1$$\bar{1}$$ 1 ¯ 0 > . Calculations indicate that the resulting strain gradients will give rise to giant flexoelectric polarization. First principles models predict that a high concentration of oxygen vacancies weaken the covalent/ionic bonds, giving rise to the unexpected plasticity. Mechanical testing on oxygen vacancies-rich Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 confirmed this prediction. These findings will facilitate the design of plastic ceramic materials and the development of flexoelectric-based nano-electromechanical systems.

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