The nano-inclusion in a matrix effectively scatters phonons and the band bending effect at the interfaces can selectively scatter carriers, resulting in the enhancement of thermoelectric performance.

Ideal electromagnetic (EM) wave absorbers can absorb all incident EM waves, regardless of the incident direction, polarization, and frequency. Absorptance and reflectance are intrinsic material properties strongly correlated with electrical conductivity; hence, achieving perfect absorptance with zero reflectance is challenging. Herein, we present a design strategy for preparing a nearly ideal EM absorber based on a layered metal that maximizes absorption by utilizing multiple internal reflections and minimizes reflection using a monotonic gradient of intrinsic impedance. This approach was experimentally verified using aluminum nanoflakes prepared via topochemical etching of lithium from Li9Al4, and the impedance-graded structure was obtained through the size-based sorting behavior of aluminum nanoflakes sinking in dispersion. Unlike in traditional shielding materials, strong absorption (26.76 dB) and negligible reflectivity (0.04 dB) with a ratio of >103 can be achieved in a 120 μm thick film. Overall, our findings exhibit potential for developing a novel class of antireflective shielding materials.

We investigated thermoelectric properties in K-doped quaternary compounds of (Pb1-xKxTe)0.70(PbSe)0.25(PbS)0.05 (x ≤ 0.03). In terms of two valence bands model, we argue that the L-band approaches to the Σ-band with increasing the K-doping concentration resulting in the increase of carrier concentration and effective mass of carrier due to the increase of band degeneracy. The effective K-doping by x = 0.02 and PbS substitution causes high power factor and low thermal conductivity, resulting in the comparatively high ZT value of 1.72 at 800 K. The low thermal conductivity for (Pb0.98K0.020Te)0.70(PbSe)0.25(PbS)0.05 compound is attributed from the lattice distortion and line dislocation in a phase of nano precipitation. By optimizing K-doping and PbS substitution, we achieved the enhancement of practical thermoelectric performance such as average ZTavg = 1.08, engineering (ZT)eng = 0.81, maximum efficiency ηmax = 11.63 %, and output power density Pd = 6.3 W cm -2 , with temperature difference ΔT = 500 K, which has practical applicability in waste heat power generation technologies.

Filled skutterudites (FSs), which are known to be good thermoelectric materials, have been intensively investigated in the field of condensed matter physics in the past decades, due to their large variety of electronic and magnetic properties. However, to the best of the authors' knowledge, there has been no previous investigation of the optical properties of FSs. The nonlinear optical saturable absorption property of FSs is investigated in this work for the first time, and the results are reported here. More specifically, Co4Sb12 is chosen as a binary skutterudite system, and indium ions are added as a filling element to form a FS of In0.2Co4Sb12. The material properties are systematically investigated using a series of measurements. Density functional theory calculations of the electronic band structures of InCo4Sb12 and In0.25Co4Sb12 are conducted for better understanding of their energy band structures. It is also demonstrated that a broadband saturable absorber (SA) that can simultaneously operate at 1.5 and 1.9 µm can readily be implemented by depositing particles of In0.2Co4Sb12 onto fiber ferrules. The efficacy of the prepared SA is tested by incorporating the device into rare earth ion‐doped fiber ring cavities, to show its capability for both 1.5 and 1.9 µm operation.

The effects of S doping at the oxygen site on the thermoelectric properties of BiOCuSe have been investigated.

This research proposes a new strategy for exploring high-performance thermoelectric materials by weak disordering of topological crystalline Dirac semimetals.

Topological insulators have attracted much interest in topological states of matter featuring unusual electrical conduction behaviors. It has been recently reported that a topological crystalline insulator could exhibit a high thermoelectric performance by breaking its crystal symmetry via chemical doping. Here, we investigate the multiple effects of Na, Se, and S alloying on thermoelectric properties of a topological crystalline insulator PbSnTe. The Na doping is known to be effective for breaking the crystalline mirror symmetry of PbSnTe. We demonstrate that simultaneous emergence of band convergence by Se alloying and nanostructuring by S doping enhance the power factor and decrease lattice thermal conductivity, respectively. Remarkably, the high power factor of 22.3 μW cm K at 800 K is achieved for Na 1%-doped PbSnTeSeS mainly due to a relatively high Seebeck coefficient via band convergence by Se alloying as well as the suppression of bipolar conduction at high temperatures by the increase of energy band gap. Furthermore, the lattice thermal conductivity is significantly suppressed by PbS nanoprecipitates without deteriorating the hole carrier mobility, ranging from 0.80 W m K for PbSnTe to 0.17 W m K at 300 K for PbSnTeSeS. As a result, the synergistically combined effects of breaking the crystalline mirror symmetry of topological crystalline insulator, band convergence, and nanostructuring for PbSnTeSe S ( x = 0, 0.05, 0.1, 0.2, and 0.95) give rise to an impressively high ZT of 1.59 at 800 K for x = 0.05. We suggest that the multiple doping in topological crystalline insulators is effective for improving the thermoelectric performance.

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