LINK - Laboratory for Innovative Key Materials and Structures

Abstract Most of the best known SnTe‐based materials exhibit an attractive thermoelectric figure of merit ( zT ) only at the high‐temperature regime, but their performance at the low‐mid temperature ranges is quite uninspiring, and this discordance necessitates a large temperature gradient (∆ T ≥ 550 K) to effectuate a reasonable efficiency, η. Here, the transition elements, Ti and Zr, that have not been used in the past are tried as dopants for SnTe and an enhanced device/average zT and/or η are reported with a lower ∆ T ≈ 400 K and without the requisite for a stupendous peak/maximum zT . This notable performance emanates from—i) improved weighted mobility by optimally balancing between effective mass, carrier concentration, and mobility, ii) coupling of charge carriers with magnetic entropy, and the paramount factor being the iii) weakening of the chemical bonds (lattice softening). The thermal damping caused by lattice softening affects the phonon group velocity and the elastic properties, and the resultant increase in the degree of anharmonicity and the high density of internal strain‐fields, along with the phonon scattering effects, play an active role in tuning the overall thermoelectric performance. This work also excavates/opens up the discussion of applying the Heikes’ equation to qualitatively compare the trend of charge carriers for a given thermoelectric material system.

A report on an improvement in the thermoelectric performance of GeTe <italic>via</italic> intentional creation of more electrically dormant Ge vacancies (in contrast to classical approaches) and modulating/balancing it with optimized Zr-doping.

The effects of laser irradiation on γ-Fe2O3 4 ± 1 nm diameter maghemite nanocrystals synthesized by co-precipitation and dispersed into an amorphous silica matrix by sol-gel methods have been investigated as function of iron oxide mass fraction. The structural properties of γ-Fe2O3 phase were carefully examined by X-ray diffraction and transmission electron microscopy. It has been shown that γ-Fe2O3 nanocrystals are isolated from each other and uniformly dispersed in silica matrix. The phase stability of maghemite nanocrystals was examined in situ under laser irradiation by Raman spectroscopy and compared with that resulting from heat treatment by X-ray diffraction. It was concluded that ε-Fe2O3 is an intermediate phase between γ-Fe2O3 and α-Fe2O3 and a series of distinct Raman vibrational bands were identified with the ε-Fe2O3 phase. The structural transformation of γ-Fe2O3 into α-Fe2O3 occurs either directly or via ε-Fe2O3, depending on the rate of nanocrystal agglomeration, the concentration of iron oxide in the nanocomposite and the properties of silica matrix. A phase diagram is established as a function of laser power density and concentration.

metal atom clusters (1 nm in diameter), successfully prepared by the microemulsion technique. This combination provides new physical insight and displays red emission in biological based solution under UV-Vis excitation with long lifetimes of around 17 and 84 μs. Moreover, the nanoparticles can be internalized by cancer cells after surface functionalization by transferrin protein and clearly imaged by TGLM under excitation at 365 nm. The nanocomposites have been mainly characterized by scanning and transmission electron microscopies (SEM and HAADF-STEM), UV-Vis and photoluminescence (PL) spectroscopies.

First fabrication of a Ta₆-based nanocomposite coating, for energy saving applications, by an EPD solution process.

) were selected to evaluate the influence of counter-cations and ligands on de-excitation mechanisms responsible for multicomponent emission of cluster units. This study evaluates the ageing of each member of the series, which is crucial for further energy conversion applications (photovoltaic, lighting, water splitting, etc.).

Abstract The first step of the integration of molybdenum clusters as new absorbers in all inorganic solar cells inspired from perovskite cells have been investigated via the fabrication of first cluster sensitized solar cells. The latter have been realized from the photoelectrodes obtained by chemisorption of the clusters on TiO 2 and NiO films (respectively named photoanodes and photocathodes). Photovoltaic characteristics reveal that photoinduced electron or hole transfers can occur from the cluster units to the n‐ or p‐type semiconductors respectively. These first photovoltaic performances highlight the interest in using this inorganic cluster as new absorber for photo‐electronical systems.

The power factor of GeSe enhanced and thermal conductivity decreased by Te substitution and thereby, GeSe_0.80Te_0.20 exhibits high <italic>ZT</italic>.

For the first time, hexanuclear complexes with general chemical formula [Ln6O(OH)8(NO3)6(H2O)n](2+) with n = 12 for Ln = Sm-Lu and Y and n = 14 for Ln = Pr and Nd were stabilized as nanoaggregates in ethylene glycol (EG). These unprecedented nanoaggregates were structurally characterized by (89)Y and (1)H NMR spectroscopy, UV-vis absorption and luminescence spectroscopies, electrospray ionization mass spectrometry, diffusion ordered spectroscopy, transmission electron microscopy, and dynamic light scattering. These nanoaggregates present a 200 nm mean solvodynamic diameter. In these nanoaggregates, hexanuclear complexes are isolated and solvated by EG molecules. The replacement of ethylene glycol by 2-hydroxybenzyl alcohol provides new nanoaggregates that present an antenna effect toward lanthanide ions. This results in a significant enhancement of the luminescence properties of the aggregates and demonstrates the suitability of the strategy for obtaining highly tunable luminescent solutions.

The thermoelectric properties of a series of Cu–Sn based thiospinel compounds by screening a variety of transition elements (M = Ti, V, Cr, Co) as a potential substituent at the Sn-site (both p- and n-type thiospionels) are reported and discussed.

The integration by a solution deposition process of tantalum octahedral clusters in multifunctional nanocomposite materials and devices for smart windows is investigated for the first time in this study.

Thermoelectric higher manganese silicides, MnSix, were synthesized by magnesioreduction followed by spark plasma sintering with different nominal compositions (x = 1.65, 1.74, and 1.80) and various postsynthesis annealing durations (0, 48, 96, and 336 h). The composite Nowotny chimney-ladder crystal structures of the resulting samples were investigated by synchrotron X-ray powder diffraction. The modulation vector component γ, generally considered corresponding to the stoichiometry (x) of the material, was accurately determined by Rietveld refinement using a (3 + 1)D superspace approach. Regardless of the initial nominal composition, all the samples have a similar γ ∼ 1.736 after 48 h of annealing at 900 K. This result suggests that MnSix, at a temperature of 900 K, is better described as a defined compound with x close to 1.736, rather than intermediate solid-solution phases with 1.725 < x < 1.75 as predicted by the commonly accepted phase diagram. At the fixed nominal composition MnSi1.74, γ increases significantly from 1.7313(2) to 1.7411(1) after 336 h of annealing, indicating that the thermal history influences the Si stoichiometry. The evolution of γ with time is concomitant with a power factor drop (−19%), attributed to a decrease in charge carrier concentration. The drop of the power factor, partially compensated by a decrease in thermal conductivity, results in a −12% reduction of the maximum figure-of-merit ZT, after prolonged annealing under realistic application conditions.

A novel UV–Vis photodetector consisting of an octahedral molybdenum cluster-functionalized Zn2Al layered double hydroxide (LDH) has been successfully synthesized by co-precipitation and delamination methods under ambient conditions. The electrophoretic deposition process has been used as a low-cost, fast, and effective method to fabricate thin and transparent nanocomposite films containing a dense and regular layered structure. The study provided evidence that the presence of the Mo6 cluster units between the LDH does not affect the ionic conduction mechanism of the LDH, which linearly depends on the relative humidity and temperature. Moreover, the photocurrent response is remarkably extended to the visible domain. The reproducibility and stabilization of the photocurrent response caused by the Mo6 cluster-functionalized LDH have been verified upon light excitation at 540 nm. Additionally, it was demonstrated that the films show advantageously strong adherence properties for application requirements.

Both n- and p-type binary Cr_2+xSe₃ were prepared by composition tuning, aiming for thermoelectric applications near room temperature.

International audience

Abstract We developed a new environment-sensing device based on the opto-ionic-electronic phenomena of an octahedral molybdenum metal (Mo 6 ) cluster. When the Mo 6 cluster is electrochemically deposited on a transparent electrode in an organic solvent containing a trace amount of water, the water permeates the deposited film. During the process, some ligand species that stabilize the frame structure of the Mo 6 cluster are substituted with hydroxyl groups, and the negatively charged frame structure of the Mo 6 cluster unit is stabilized by hydronium counterions. As a result, the transparent film of the Mo 6 cluster fabricated by this method exhibits ionic-electronic mixed conduction of the hydronium ion. The ionic conduction greatly changes depending on the temperature and humidity in the atmosphere, and the electrical conductivity greatly changes depending on the wavelength and intensity of the irradiated light. These unique multisensing properties present new possibilities for environmental sensing applications.

A Co9S8 dense ceramic sintered by spark plasma sintering has been characterized by X-ray powder diffraction and transmission electron microscopy (diffraction and high resolution). This allowed magnetic, electronic, and thermal transport measurements to be made for a cubic (a = 9.927(2)Å) Co9S8 sample free of impurities and structural defects. The magnetic susceptibility and magnetic field dependence of the magnetization point toward an antiferromagnetic state, whereas the four-probe resistivity reveals a very metallic behavior with ρ300 K = 80 μΩ.cm described by a classical electron phonon model. When compared to CoS2, even if Co9S8 exhibits lower ρ values associated with the lack of ferromagnetic fluctuations existing in the former, the Co9S8 thermoelectric power factor, negative as in CoS2, is smaller, nonetheless leading to a power factor (PF) reaching PF ≈ 0.5 mW m–1 K–2 at 300 K. In Co9S8, with its low ρ going with a very high electronic part of the thermal conductivity κ, the lattice part of κ is smaller than that of CoS2 (∼2 W m–1 K–1 for Co9S8 at 300 K) suggesting that the more complex structure of Co9S8, with two different types of CoSn polyhedra, plays an important role.

Thin and transparent Mo6 cluster films with significant optical properties were prepared on indium tin oxide (ITO)-coated glass plates from the suspension of Cs2Mo6Br14 cluster precursors dispersed in methyl-ethyl-ketone (MEK) by an electrophoretic deposition (EPD) process. Two kinds of polydimethylsiloxanes (PDMS); i.e., KF-96L-1.5CS and KF-96L-2CS corresponding to the kinetic viscosity of 1.5 and 2 centistokes, respectively, were selected to topcoat the Mo6 cluster film after the EPD. The influence of the PDMS on the durability, chemical compatibility and light absorption property of Mo6 cluster films were characterized by means of field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. The stabilized PDMS-coated Mo6 cluster film could be stored for more than 6 months under ambient conditions.

Mobility of <italic>n</italic>Fe₃O₄@DMSA within natural soil is higher than uncoated <italic>n</italic>Fe₃O₄ which impacts differently the mobility of TEs and NOM.

The crucial role of solubilization and crystallization steps in the vibrational and optical properties of {Ta6Bri12} cluster core containing systems.