Gabin Guélou

CRISMAT - CNRS

In-filled skutterudites In x Co 4 Sb 12 have attracted much attention due to their relatively high thermoelectric performance, which, in turn, is attributed to the In atoms acting as rattlers in the skutterudite voids...

Research focusing on the interplay between structural features and transport properties in inorganic materials is of paramount importance for the identification, comprehension and optimisation of functional materials. In this respect, Earth-abundant copper sulphides have been receiving considerable attention from scientists as the urgency remains t...

Research focusing on the interplay between structural features and transport properties of inorganic materials is of paramount importance for the identification, comprehension, and optimisation of functional materials. In this respect, Earth‐abundant copper sulfides have been receiving considerable attention from scientists as the urgency remains t...

The quaternary sulphide V-Sn colusite, Cu26V2Sn6S32, is one of the most promising cost-efficient thermoelectric materials to date because of the low toxicity, wide availability and low cost of the composing elements. Recent studies have demonstrated the potential of this environmentally-friendly material and its transport properties are now well un...

Regardless the complexity of the phase diagram of the Cu-Sn-S system, several compositions near the prototypical mohite Cu2SnS3 have arisen as potential non-toxic, earth-abundant and cost-efficient photovoltaic and thermoelectric materials....

Derivatives of the natural mineral colusite with general formula Cu26A2E6S32 (A = V, Nb, Ta, Cr, Mo, W; E = Ge, Sn, As, Sb), are an emerging class of excellent thermoelectric materials. Within just a few years, they have been promoted as serious candidates for cost-efficient, environmentally-friendly thermoelectric power generation, reaching perfor...

A pristine colusite Cu26V2Sn6S32 was successfully synthesised on a 100 g scale via a mechanochemical reaction in an industrial eccentric vibratory ball mill followed by spark plasma sintering (SPS) at 873 K. The milling of elemental precursors from 1 up to 12 hours was performed and the prepared samples were investigated in detail by X-ray powder d...

Thermoelectric colusites, one of the most recently identified and most promising family of complex Cu–S materials, have quickly attracted significant attention based on their outstanding performance. Herein, we investigate the effect of zinc for copper substitution on the thermoelectric properties of the high-performance Cr–Ge colusite, Cu26Cr2Ge6S...

Herein, we demonstrate that BiCuSeO compound can be formed in bulk directly from the raw materials through reactive spark plasma sintering (RSPS) followed by ball milling and a second short spark plasma sintering step. Compared to BiCuSeO samples obtained by a conventional solid-state reaction, the electrical transport properties of the RSPS bulk w...

In recent years, thermoelectric materials inspired from the natural mineral colusite have emerged as a new class of environmentally-friendly copper-based sulfides composed of abundant elements. Herein, high performance bulk colusite Cu26V2Sn6S32 materials were synthesized using mechanical alloying and spark plasma sintering of low-cost industrial-g...

Herein, we demonstrate that BiCuSeO compound can be formed in bulk directly from the raw materials through reactive spark plasma sintering (RSPS) followed by ball milling and a second short spark plasma sintering step. Compared to BiCuSeO samples obtained by a conventional solid-state reaction, the electrical transport properties of the RSPS bulk w...

Cation over-stoichiometry in the high-performance thermoelectric colusite, [Cu26Cr2Ge6]1+δS32, is a successful approach to modify the conduction mechanism and optimize the charge carrier concentration. This functionalization of the “Cu26S32” conductive network leads to a record figure of merit of 1.0 at 700 K among ternary and quaternary sulfides.

Ca3Co4O9 + xwt.% TiC (x = 0, 0.25, 0.5, 0.75, and 1.0) polycrystalline thermoelectric ceramics have been prepared through the classical ceramic route. XRD characterization has demonstrated that all samples are mainly composed by the Ca3Co4O9 phase, while microstructural observation has shown that no reaction between both components has been produce...

This paper describes the influence of the powder synthesis and densification techniques on the structure, microstructure and thermoelectric properties of Cu22Fe8Ge4S32, a synthetic derivative of the naturally occurring germanite mineral. Two powder synthesis approaches are compared, namely mechanical alloying and conventional sealed tube synthesis,...

The influence of structural disorder on the thermal transport in the colusite Cu26V2Sn6S32 has been investigated by means of low-temperature thermal conductivity and specific heat measurements (2–300 K), Sn119 Mössbauer spectroscopy and temperature-dependent powder inelastic neutron scattering (INS). Variations in the high-temperature synthesis con...

The effect of excess Te in the preparation of synthetic mineral paracostibite, CoSbS, was investigated in an attempt to produce a nano-micro-porous architecture. While the latter was found to have no significant impact, we demonstrate that such strategy is a successful approach to enhance both electrical and thermal property via the formation of a...

A complete study on the thermal stability of the crystal structure and electrical properties, as well as on the phase decomposition, of the high performance thermoelectric colusite Cu26Cr2Ge6S32 is presented. Combination of results from differential scanning calorimetry, thermogravimetric analysis, in situ neutron powder diffraction, and Seebeck co...

Sulfide-based materials are emerging as viable alternatives for the current state-of-the-art thermoelectric materials, which usually are composed of toxic, expensive and scarce elements. Here, a systematic study of one such inexpensive and environmentally friendly sulfide-based system, i.e. Fe7-xCoxS8 pyrrhotite-type compounds that were synthesized...

Copper-rich sulfides with the composition Cu22-xZnxFe8Ge4S32 (0 ≤ x ≤ 2) have been investigated. The detailed structural study combining powder X-ray diffraction, electron microscopy and Mössbauer spectroscopy shows a crossover from a germanite-type domain for 0 ≤ x ≤ 0.4 to a renierite-type domain for 1.2 ≤ x ≤ 2.0, with a biphasic region around x...

Herein, we investigate the Mo and W substitution for Cr in synthetic colusite, Cu26Cr2Ge6S32. Primarily, we elucidate the origin of extremely low electrical resistivity which does not compromise the Seebeck coefficient and leads to outstanding power factors of 1.94 mW m⁻¹ K⁻² at 700 K in Cu26Cr2Ge6S32. We demonstrate that the abnormally long iono‐c...

In the present study, we investigate the Mo and W for Cr substitution in the synthetic mineral colusite, Cu26Cr2Ge6S32. Primarily, we elucidate the origin of extremely low electrical resistivity which does not compromise the Seebeck coefficient and leads to outstanding power factors of 1.94 mW m‐1 K‐2 at 700 K in Cu26Cr2Ge6S32. We demonstrate that...

The crystal structure of the tetrahedrites Cu12 − xMnxSb4S13 (x = 0, 1) has been studied by powder neutron diffraction between room temperature and 773 K. At all temperatures investigated, manganese exclusively occupies tetrahedral sites, while the trigonal-planar sites contain only copper. In situ diffraction data confirm the stability of the tetr...

Bi1-xNdxCuSeO (x = 0; 0.05; 0.10; 0.15) was fabricated by the solid-state reaction and the reactive spark plasma sintering for comparative study. It was demonstrated that BiCuSeO could be formed in-situ by the reaction between Bi2O3, Bi, Cu and Se during the densification process. The effect of Nd doping on the thermoelectric properties has been in...

Considering that more than half of all primary energy, i.e. fossil fuels, that mankind consumes is lost in the form of waste heat, the solid state conversion of heat to electricity that thermoelectric materials represent through the Seebeck effect can have a huge benefit to society (Koumoto and Mori 2013, Mori and Nolas 2016). However, it is not ea...

We synthesized new series of layered copper oxytellurides Sr2TMCu2Te2O2 with variation in transition metal (TM= Mn, Co, Zn) elements. These compounds are the first example having alternately stacked anti-fluorite Cu2Te2 layer and perovskite-like TM-oxide layer. Reflecting the longer ionic radius of Te than Se and S, it exhibits larger lattice param...

Thin films of YbB4 and YbB6 have been deposited on sapphire substrates via hybrid physical chemical vapor deposition (HPCVD) using elemental ytterbium and decaborane, B10H14, as sources. The deposition condition dependence of the composition, purity, crystallinity and electrical properties has been investigated using x-ray diffraction (XRD), reflec...

Tetrahedrites are promising p-type thermoelectric materials for energy recovery. We present here the first investigation of the structure and thermoelectric properties of copper-rich tetrahedrites, Cu12+xSb4S13 (0 < x ≤ 2.0). At room temperature, all samples with x > 0 consist of two tetrahedrite phases. In-situ neutron diffraction data demonstrate...

A family of phases, Co x TiS2 (0 ≤ x ≤ 0.75) has been prepared and characterised by powder X-ray and neutron diffraction, electrical and thermal transport property measurements, thermal analysis and SQUID magnetometry. With increasing cobalt content, the structure evolves from a disordered arrangement of cobalt ions in octahedral sites located in...

The scale up of Spark Plasma Sintering (SPS) for the consolidation of large square monoliths (50 × 50 × 3 mm3) of thermoelectric material is demonstrated and the properties of the fabricated samples compared with those from laboratory scale SPS. The SPS processing of n-type TiS2 and p-type Cu10.4Ni1.6Sb4S13 produces highly dense compacts of phase p...

Bulk polycrystalline samples in the series Ti1-xNb x S2 (0≤ x ≤0.075) were prepared using mechanical alloying synthesis and spark plasma sintering. X-ray diffraction analysis coupled with high resolution transmission electron microscopy indicates the formation of trigonal TiS2 by high energy ball-milling. The as-synthesized particles consist of pse...

Understanding the underlying mechanisms that suppress thermal conduction in solids is of paramount importance for the targeted design of materials for thermal management and thermoelectric energy conversion applications. Bismuth copper oxychalcogenides, BiOCuQ (Q = Se, Te), are highly crystalline thermoelectric materials with an unusually low latti...

Over the past 2 years, silicon nanoparticles (SiNPs) functionalised with conjugated molecules have been shown to have potential as low-temperature thermoelectric materials. One key challenge with such materials relates to the introduction of charge carriers. There are two components of organic/silicon nanocomposite materials in which charge carrier...

Bornite, Cu5FeS4, is a naturally-occurring mineral with an ultralow thermal conductivity and potential for thermoelectric power generation. We describe here a new, easy and scalable route for synthesising bornite, together with the thermoelectric behaviour of manganese-substituted derivatives, Cu5Fe1−xMnxS4 (0 ≤ x ≤ 0.10). The electrical and therma...

Bulk polycrystalline samples in the series Ti1+xS2 (x = 0 to x = 0.05) were prepared using high-temperature synthesis from the elements and spark plasma sintering. X-ray structure analysis shows that the lattice constant c expands as titanium intercalates between TiS2 slabs. A Seebeck coefficient close to −300 μV K−1 is observed for the first time...

The new thermoelectric material BiOCuTe exhibits an electrical conductivity of 224 S cm−1 and a Seebeck coefficient of +186 μV K−1 at 373 K, together with an extremely low lattice thermal conductivity of [similar]0.5 W m−1 K−1. This results in a ZT of 0.42 at 373 K, which increases to 0.66 at the maximum temperature investigated, 673 K.