Explore the vast range of titles available.

Half-Heusler compounds have been in focus as potential materials for thermoelectric energy conversion in the mid-temperature range, e.g., as in automotive or industrial waste heat recovery, for more than ten years now. Because of their mechanical and thermal stability, these compounds are advantageous for common thermoelectric materials such as Bi 2 Te 3 , SiGe, clathrates or filled skutterudites. A further advantage lies in the tunability of Heusler compounds, allowing one to avoid expensive and toxic elements. Half-Heusler compounds usually exhibit a high electrical conductivity σ , resulting in high power factors. The main drawback of half-Heusler compounds is their high lattice thermal conductivity. Here, we present a detailed study of the phase separation in an n-type Heusler materials system, showing that the Ti x Zr y Hf z NiSn system is not a solid solution. We also show that this phase separation is key to the thermoelectric high efficiency of n-type Heusler materials. These results strongly underline the importance of phase separation as a powerful tool for designing highly efficient materials for thermoelectric applications that fulfill the industrial demands of a thermoelectric converter.

The present work elaborates on the correlation between the amount and ordering of the free carbon phase in silicon oxycarbides and their charge carrier transport behavior. Thus, silicon oxycarbides possessing free carbon contents from 0 to ca. 58 vol.% (SiOC/C) were synthesized and exposed to temperatures from 1100 to 1800 °C. The prepared samples were extensively analyzed concerning the thermal evolution of the sp2 carbon phase by means of Raman spectroscopy. Additionally, electrical conductivity and Hall measurements were performed and correlated with the structural information obtained from the Raman spectroscopic investigation. It is shown that the percolation threshold in SiOC/C samples depends on the temperature of their thermal treatment, varying from ca. 20 vol.% in the samples prepared at 1100 °C to ca. 6 vol.% for the samples annealed at 1600 °C. Moreover, three different conduction regimes are identified in SiOC/C, depending on its sp2 carbon content: (i) at low carbon contents (i.e., <1 vol.%), the silicon oxycarbide glassy matrix dominates the charge carrier transport, which exhibits an activation energy of ca. 1 eV and occurs within localized states, presumably dangling bonds; (ii) near the percolation threshold, tunneling or hopping of charge carriers between spatially separated sp2 carbon precipitates appear to be responsible for the electrical conductivity; (iii) whereas above the percolation threshold, the charge carrier transport is only weakly activated (Ea = 0.03 eV) and is realized through the (continuous) carbon phase. Hall measurements on SiOC/C samples above the percolation threshold indicate p-type carriers mainly contributing to conduction. Their density is shown to vary with the sp2 carbon content in the range from 1014 to 1019 cm−3; whereas their mobility (ca. 3 cm2/V) seems to not depend on the sp2 carbon content.

N-type half-Heusler NbCoSn is a promising thermoelectric material due to favourable electronic properties. It has attracted much attention for thermoelectric applications while the desired p-type NbCoSn counterpart shows poor thermoelectric performance. In this work, p-type NbCoSn has been obtained using Sc substitution at the Nb site, and their thermoelectric properties were investigated. Of all samples, Nb 0.95 Sc 0.05 CoSn compound shows a maximum power factor of 0.54 mW/mK 2 which is the highest among the previously reported values of p-type NbCoSn. With the suppression of thermal conductivity, p-type Nb 0.95 Sc 0.05 CoSn compound shows the highest measured figure of merit ZT = 0.13 at 879 K.

Half-Heusler (HH) compounds are some of the most promising candidates among the medium-temperature thermoelectric materials being investigated for automotive and industrial waste heat recovery applications. For n - as well as p -type material, peak ZT values larger than one have been published recently, and first modules have been built. The next step to facilitate the industrialization of thermoelectric module production is upscaling of material synthesis. In this paper, the latest results of the thermoelectric properties of HH compounds produced in kg batches are presented and compared with values published in the literature. The performance of modules built from these materials is analyzed with respect to power output and long-term stability of the material and electrical contacts.

Ideally, once batteries reach their end‐of‐life, they are expected to be collected, dismantled, and converted into black mass (BM), which contains significant amounts of valuable metals. BM can be regarded as a sort of urban mine, where recyclers extract and reintroduce the materials into new battery manufacturing. Focusing on BM, this article discusses the necessity of BM recovery and current recycling situations. Although the benefits of recycling are widely acknowledged, many challenges and issues remain. The BM market is still in its infancy and relevant regulatory frameworks need to be updated with respect to the widespread use and advancement of lithium‐ion batteries. Current BM producing and processing technologies are gaining momentum and still have room for large improvements in terms of economic feasibility and environmental footprint. Finding solutions for these challenges in the end requires efforts from both researchers and industrial stakeholders with growing interests and long‐term patient engagement. Battery regulations and legal support are highly anticipated for industries to keep high levels of commitment to long‐term investments. Closed loop of black mass recovery (processing in blue, products in green).

As numerous studies on highly efficient perovskite solar cells have been conducted on lead‐based light absorbers, such as MAPbI3 and FAPbI3, increasing concerns are rising regarding toxicity and stability issues. One of the most prominent and promising lead‐free alternatives is the double‐perovskite Cs2AgBiBr6, which is well‐suited for multi‐junction solar cells considering its relatively large indirect bandgap of around 1.95–2.05 eV. Despite distinctive reports on its performance under ambient conditions, the demonstrated stability has not yet been conclusively clarified. Within this study, the degradation behavior of Cs2AgBiBr6 single crystals is investigated under different ambient environments, such as AM1.5g solar irradiation, aquatic conditions, and humidity. The corresponding samples are analyzed by using Raman, UV–vis, energy‐dispersive X‐Ray, and micro‐photoluminescence spectroscopies together with X‐Ray diffraction. High intrinsic stability of Cs2AgBiBr6 in ambient conditions and severe degradation in aquatic conditions are observed. Furthermore, surface morphology alterations are found during the simulated solar irradiation indicating photo‐accelerated degradation behavior. In the results of this study, it is clearly implied that intense research efforts need to be put into sealing the Cs2AgBiBr6 layer in solar cells with the goal of protecting it from humidity and water intrusion simultaneously, therefore avoiding photo‐accelerated degradation. Cs2AgBiBr6 is investigated as a lead‐free solar absorber. However, opinions diverge when addressing the material's stability. In this study, the behavior of Cs2AgBiBr6 single crystals under different ambient conditions is simulated and investigated with UV–vis, Raman, micro‐photoluminescence, scanning electron microscope energy‐dispersive X‐ray spectroscopies, and powder X‐ray diffraction. Heavy sample deterioration and photodegradation are demonstrated, and degradation pathways are suggested. Furthermore, the first regenerative synthesis of Cs2AgBiBr6 is reported.

Half-Heusler (HH) and especially TiNiSn-based alloys have shown high potential as thermoelectric (TE) materials for power generation applications. The reported transport properties show, however, a significant spread of results, due mainly to the difficulty in fabricating single-phase HH samples in these multicomponent and multiphased systems. In particular, little attention has been paid to the influence of the various minority phases on the TE performance of these compounds. A clear understanding of these issues is mandatory for the design of improved and stable TE HH-based composites. This study examines the structural and compositional influence of the residual metallic (Sn) and intermetallic phases (mainly Ti6Sn5 and the Heusler compound TiNi2Sn) on the TE properties of the TiNiSn HH compounds processed by spark plasma sintering.

Pb‐free halide perovskites have recently attracted immense attention due to the number of advantages in their optical and electronic properties. However, tuning the optical bandgap with minimized amounts of point defects is a particularly challenging task in photovoltaics. It is pivotal to clearly understand the detailed relationship between the bandgap change with defect generation and charge carrier lifetime. In this study, Cs3Sb2I9 crystals are synthesized by varied choice of solvents, namely, γ‐butyrolactone, a mixture of dimethylformamide and dimethyl sulfoxide, and hydroiodic acid. Although the same principles of decreasing solubility and crystallization are applied, Cs3Sb2I9 crystals with different size and shape in microscopic and macroscopic scale are obtained during heating and cooling of the solution. The synthesized crystals are investigated using a combination of different spectroscopies including Raman, UV–visible, and time‐resolved photoluminescence. In the results, it is suggested that there is a strong relationship between Urbach energy and the lifetime of charge carriers. In this research, readily applicable practical principles and examples of how to control the defects for the advancement in Pb‐free perovskite photovoltaics are provided. Cs3Sb2I9 crystals are synthesized by varied choice of solvents, namely, γ‐butyrolactone (GBL), a mixture of dimethylformamide and dimethyl sulfoxide, and hydroiodic acid. Different colors of crystals are obtained depending on the solvent used. In the end, GBL is found to be not only more ecologically feasible compared to acidic solvent, but also more favorable within the investigated hydrothermal synthesis condition.

Lithium is in high demand: this is driven by current trends in e-mobility and results in increased global production and record prices for lithium ores and compounds. Pegmatite ores, in addition to brines, remain of particular interest because of their higher lithium content and lower geopolitical risks. In this work, we investigated lithium extraction via the mechanochemical treatment of the three most common lithium minerals: lepidolite, spodumene, and petalite. Indeed, we determine that the petalite crystal structure was much more suitable due to its less dense packing and the formation of cleavage planes along lithium sites, resulting in substantial lithium extraction of 84.9% and almost complete conversion to hydrosodalite after 120 min of ball milling in alkaline media. Further processing of the leach liquor includes desilication, the precipitation of lithium phosphate, and the conversion and crystallization of pure LiOH·H2O. Special attention was paid to a holistic approach entailing the generation of by-products, each of which has a specific intended application. The leaching residues were investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption/desorption, and scanning electron microscopy. Moreover, hydrosodalite was found to have a high potential as an adsorbent for heavy metal ions which were studied separately using aqueous solutions containing Cu2+, Ni2+, Pb2+, and Zn2+.

The amount and type of defects in Cs2AgBiBr6 are controlled by varying the Ag/Bi ratio of the precursor solutions in two different synthesis routes, that is, slow solution cooling crystallization and fast microwave‐assisted hydrothermal synthesis. The correlation between the Ag/Bi ratio in the precursor solution and defect formation in the crystals is studied by band broadening analysis in Raman spectroscopy, the estimated Urbach energy in UV–vis spectroscopy, and thermogravimetric analysis. Ag‐rich precursors are found to prevent the formation of the secondary‐phase Cs3Bi2Br9, but at the same time induced the formation of Br vacancies and antisite defects. Time‐resolved photoluminescence measurements reveal that the formation of beneficial defects such as Br vacancies causes to trap the charge carriers, thus avoiding the recombination of charge carriers and leading to a longer carrier lifetime. Herein, the findings provide a guidance to decrease the defect densities and can be applied to the fabrication of Pb‐free solar cells based on Cs2AgBiBr6. Schematic illustration of the induced dominant defects for Bi‐rich/stoichiometric conditions and Ag‐rich conditions. Light absorption, emission, and trapping/detrapping mechanisms of charge carriers are highlighted.