Surface Degradation of MgX-Based Composites at Room Temperature: Assessing Grain Boundary and Bulk Diffusion Using Atomic Force Microscopy and Scanning Electron Microscopy.

Practical application of thermoelectric generators necessitates materials that combine high heat-to-electricity conversion efficiency with long-term functional stability under operation conditions. While Mg(Si,Sn)-based materials exhibit promising thermoelectric properties and module prototypes have been demonstrated, their stability remains a challenge, demanding thorough investigation. Utilizing atomic force microscopy (AFM) and scanning electron microscopy (SEM), we investigate the surface degradation of a composite material comprising Si-rich and Sn-rich Mg(Si,Sn) solid solutions.

Impact of the Dopant Species on the Thermomechanical Material Properties of Thermoelectric MgSiSn.

Thermoelectric generators are an excellent option for waste heat reuse. Materials for such devices have seen their thermoelectric properties improving constantly. The functioning of a generator, however, does not only depend on thermoelectric properties.

Overcoming Asymmetric Contact Resistances in Al-Contacted Mg(Si,Sn) Thermoelectric Legs.

Thermoelectric generators are a reliable and environmentally friendly source of electrical energy. A crucial step for their development is the maximization of their efficiency. The efficiency of a TEG is inversely related to its electrical contact resistance, which it is therefore essential to minimize.

Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators.

The efficiency of a thermoelectric (TE) generator for the conversion of thermal energy into electrical energy can be easily but roughly estimated using a constant properties model (CPM) developed by Ioffe. However, material properties are, in general, temperature (T)-dependent and the CPM yields meaningful estimates only if physically appropriate averages, i.e.

Non-Rigid Band Structure in MgGe for Improved Thermoelectric Performance.

Magnesium silicide and its solid solutions are among the most attractive materials for thermoelectric generators in the temperature range of 500-800 K. However, while n-type Mg(Si,Ge,Sn) materials show excellent thermoelectric performance, the corresponding p-type solid solutions are still inferior, mainly due to less favorable properties of the valence bands compared to the conduction bands. Here, Li doped MgGe with a thermoelectric figure of merit zT of 0.

Developing Contacting Solutions for MgSiSn-Based Thermoelectric Generators: Cu and NiCu as Potential Contacting Electrodes.

Magnesium silicides can be used for thermoelectric energy conversion as high values of figure of merit zT were obtained for n-type (1.4 at 500 °C) and p-type (0.55 at 350 °C) materials.

High efficiency Mg(Si,Sn)-based thermoelectric materials: scale-up synthesis, functional homogeneity, and thermal stability.

Considering the need for large quantities of high efficiency thermoelectric materials for industrial applications, a scalable synthesis method for high performance magnesium silicide based materials is proposed. The synthesis procedure consists of a melting step followed by high energy ball milling. All the materials synthesized this method demonstrated not only high functional homogeneity but also high electrical conductivity and Seebeck coefficients of around 1000 Ω cm and -200 μV K at 773 K, respectively.

Insight on the Interplay between Synthesis Conditions and Thermoelectric Properties of α-MgAgSb.

α-MgAgSb is a very promising thermoelectric material with excellent thermoelectric properties between room temperature and 300 °C, a range where few other thermoelectric materials show good performance. Previous reports rely on a two-step ball-milling process and/or time-consuming annealing. Aiming for a faster and scalable fabrication route, herein, we investigated other potential synthesis routes and their impact on the thermoelectric properties of α-MgAgSb.

Dispersion of Multi-Walled Carbon Nanotubes in Skutterudites and Its Effect on Thermoelectric and Mechanical Properties.

Filled cobalt-antimony based skutterudites have proven themselves as very promising thermoelectric materials for generator applications in an intermediate temperature range between 400 and 800 K due to their high figure of merit. Besides the functional thermoelectric properties also the skutterudites’ mechanical properties play an important role to withstand external mechanical and internal thermomechanical loads during operation. Properties of interest are hardness as well as fracture toughness and resistance to fatigue.

On the True Indium Content of In-Filled Skutterudites.

The incongruently melting single-filled skutterudite InxCo4Sb12 is known as a promising bulk thermoelectric material. However, the products of current bulk syntheses contain always impurities of InSb, Sb, CoSb, or CoSb2, which prevent an unbiased determination of its thermoelectric properties. We report a new two-step synthesis of high-purity InxCo4Sb12 with nominal compositions x = 0.

Layered germanium tin antimony tellurides: element distribution, nanostructures and thermoelectric properties.

In the system Ge-Sn-Sb-Te, there is a complete solid solution series between GeSb2Te4 and SnSb2Te4. As Sn2Sb2Te5 does not exist, Sn can only partially replace Ge in Ge2Sb2Te5; samples with 75% or more Sn are not homogeneous. The joint refinement of high-resolution synchrotron data measured at the K-absorption edges of Sn, Sb and Te combined with data measured at off-edge wavelengths unambiguously yields the element distribution in 21R-Ge(0.

The solid solution series (GeTe)x(LiSbTe2)2 (1 ≤ x ≤ 11) and the thermoelectric properties of (GeTe)11(LiSbTe2)2.

Exchanging one Ge(2+) with two Li(+) per formula unit in (GeTe)n(Sb2Te3) (n = 1, 2, 3, ...

Ag-assisted CBE growth of ordered InSb nanowire arrays.

We present growth studies of InSb nanowires grown directly on [Formula: see text] and [Formula: see text] substrates. The nanowires were synthesized in a chemical beam epitaxy (CBE) system and are of cubic zinc blende structure. To initiate nanowire nucleation we used lithographically positioned silver (Ag) seed particles.

Sub-50 nm patterning by immersion interference lithography using a Littrow prism as a Lloyd's interferometer.

We present a simple setup that combines immersion lithography with a Lloyd's mirror interferometer. Aiming for smaller structure sizes, we have replaced the usual Lloyd's interferometer by a triangular Littrow prism with one metal-coated side, which acts as a mirror. Because of the higher refractive index of the prism, the wavelength and, thus, the attainable structure sizes, are decreased significantly.

Metal-assisted chemical etching of silicon: a review.

This article presents an overview of the essential aspects in the fabrication of silicon and some silicon/germanium nanostructures by metal-assisted chemical etching. First, the basic process and mechanism of metal-assisted chemical etching is introduced. Then, the various influences of the noble metal, the etchant, temperature, illumination, and intrinsic properties of the silicon substrate (e.

Sub-100 nm silicon nanowires by laser interference lithography and metal-assisted etching.

By combining laser interference lithography and metal-assisted etching we were able to produce arrays of silicon nanowires with uniform diameters as small as 65 nm and densities exceeding 2 x 10(7) mm(-2). The wires are single crystalline, vertically aligned, arranged in a square pattern and obey strict periodicity over several cm(2). The applied technique allows for a tailoring of nanowire size and density.

Sub-20 nm Si/Ge superlattice nanowires by metal-assisted etching.

An effective and low-cost method to fabricate hexagonally patterned, vertically aligned Si/Ge superlattice nanowires with diameters below 20 nm is presented. By combining the growth of Si/Ge superlattices by molecular beam epitaxy, prepatterning the substrate by anodic aluminum oxide masks, and finally metal-assisted chemical wet etching, this method generates highly ordered hexagonally patterned nanowires. This technique allows the fabrication of nanowires with a high area density of 10(10) wires/cm(2), including the control of their diameter and length.

Three-beam interference lithography: upgrading a Lloyd's interferometer for single-exposure hexagonal patterning.

Three-beam interference lithography is used to create hole/dot photoresist patterns with hexagonal symmetry. This is achieved by modifying a standard two-beam Lloyd's mirror interferometer into a three-beam interferometer, with the position of the mirrors chosen to guarantee 120 degrees symmetry of exposure. Compared to commonly used three-beam setups, this brings the advantage of simplified alignment, as the position of the mirrors with respect to the substrate is fixed.