May 10, 2023

Enhanced Thermoelectric Performance of Nanostructured Cu2SnS3 (CTS) via Ag Doping

Ketan Lohani, Himanshu Nautiyal, Narges Ataollahi, Umberto Anselmi-Tamburini Umberto Anselmi-Tamburini, Carlo Fanciulli, and Paolo Scardi

ACS Appl. Nano Mater. 2023, 6, 7, 6323–6333

https://doi.org/10.1021/acsanm.3c00716

Abstract

The present work aims to investigate the effect of Ag doping on the thermoelectric properties of Cu2SnS3 (CTS). Various Cu2Ag(x)Sn(1–x)S3 (0.05 ≤ x ≤ 0.25) samples were synthesized by mechanical alloying followed by spark plasma sintering, and their structural and transport properties were systematically investigated. The x = 0.15 sample presented a ∼10-fold higher power factor than the undoped CTS. Although, the x = 0.125 sample had a lower power factor than the x = 0.15 sample, owing to its lower thermal conductivity, both the samples showed the highest zT ∼ 0.8 at 723 K. This value is comparable to the best results available in the literature for earth-abundant and eco-friendly thermoelectric materials. Interestingly, the thermal conductivity of Cu2Ag(x)Sn(1–x)S3 samples increased with Ag substitution, which was further investigated using the first-principles and ab initio molecular dynamics calculations. It was observed that the incorporation of Ag into the system decreases the root mean square displacement of the other cations and anions, reducing the scattering of phonons and thereby increasing the lattice thermal conductivity. Moreover, the calculations on the formation energy have revealed the reason for the structural transformation of CTS and similar diamond-like structures toward high symmetry polymorphs by external doping. The increase in zT is directly related to the optimization of the band gap and the weighted mobility, which have been investigated experimentally and using the first principle method.

Keywords: :Cu2SnS3 copper tin sulfide CTS thermoelectricity chalcogenides mechanical alloying spark plasma sintering lattice thermal conductivity weighted mobility DFT AIMD

X-ray powder diffraction in education. Part II. Intensity of a powder pattern

Robert Dinnebier and Paolo Scardi

Journal of applied crystallography
Volume 56, 9 May 2023

https://doi.org/10.1107/S1600576723002121

Abstract

This article is the second part of a series dealing with the description and visualization of mathematical functions used to describe a powder diffraction pattern for teaching and education purposes. The first part dealt with the instrumental and sample contributions to the profile of a Bragg peak [Dinnebier & Scardi (2021). J. Appl. Cryst. 54, 1811–1831]. The second part, here, deals with the mathematics and physics of the intensity in X-ray powder diffraction. Scholarly scripts are again provided using the Wolfram language in Mathematica.

Keywords: powder diffraction; peak intensity; intensity corrections; powder patterns; Mathematica.
 

Roadmap on thermoelectricity

Cristina Artini, Giovanni Pennelli, Patrizio Graziosi, Zhen Li, Neophytos Neophytou, Claudio Melis, Luciano Colombo, Eleonora Isotta, Ketan Lohani, Paolo Scardi, Alberto Castellero, Marcello Baricco, Mauro Palumbo, Silvia Casassa, Lorenzo Maschio, Marcella Pani, Giovanna Latronico, Paolo Mele, Francesca Di Benedetto, Gaetano Contento, Maria Federica De Riccardis, Raffaele Fucci, Barbara Palazzo, Antonella Rizzo, Valeria Demontis, Domenic Prete, Muhammad Isram, Francesco Rossella, Alberto Ferrario, Alvise Miozzo, Stefano Boldrini, Elisabetta Dimaggio, Marcello Franzini, Simone Galliano, Claudia Barolo, Saeed Mardi, Andrea Reale, Bruno Lorenzi, Dario Narducci, Vanira Trifiletti, Silvia Milita, Alessandro Bellucci and Daniele M Trucchi

Nanotechnology, Volume 34, 9 May 2023, 292001

https://doi.org/10.1088/1361-6528/acca88

Abstract

The increasing energy demand and the ever more pressing need for clean technologies of energy conversion pose one of the most urgent and complicated issues of our age. Thermoelectricity, namely the direct conversion of waste heat into electricity, is a promising technique based on a long-standing physical phenomenon, which still has not fully developed its potential, mainly due to the low efficiency of the process. In order to improve the thermoelectric performance, a huge effort is being made by physicists, materials scientists and engineers, with the primary aims of better understanding the fundamental issues ruling the improvement of the thermoelectric figure of merit, and finally building the most efficient thermoelectric devices. In this Roadmap an overview is given about the most recent experimental and computational results obtained within the Italian research community on the optimization of composition and morphology of some thermoelectric materials, as well as on the design of thermoelectric and hybrid thermoelectric/photovoltaic devices.
 

Keywords: thermoelectricity, thermoelectric materials, thermoelectric devices, heat transport, electronic transport, modelling

January 16, 2023

Mechanochemical Synthesis of Sustainable Ternary and Quaternary Nanostructured Cu2SnS3, Cu2ZnSnS4, and Cu2ZnSnSe4 Chalcogenides for Thermoelectric Applications

Himanshu Nautiyal, Ketan Lohani, Binayak Mukherjee, Eleonora Isotta, Marcelo AugustoMalagutti, Narges Ataollahi, Ilaria Pallecchi, Marina Putti, Scott T. Misture, Luca Rebuffi and Paolo Scardi
https://doi.org/10.3390/nano13020366

Abstract
Copper-based chalcogenides have emerged as promising thermoelectric materials due to their high thermoelectric performance, tunable transport properties, earth abundance and low toxicity. We have presented an overview of experimental results and first-principal calculations investigating the thermoelectric properties of various polymorphs of Cu2SnS3 (CTS), Cu2ZnSnS4 (CZTS), and Cu2ZnSnSe4 (CZTSe) synthesized by high-energy reactive mechanical alloying (ball milling). Of particular interest are the disordered polymorphs of these materials, which exhibit phonon-glass–electron-crystal behavior—a decoupling of electron and phonon transport properties. The interplay of cationic disorder and nanostructuring leads to ultra-low thermal conductivities while enhancing electronic transport. These beneficial transport properties are the consequence of a plethora of features, including trap states, anharmonicity, rattling, and conductive surface states, both topologically trivial and non-trivial. Based on experimental results and computational methods, this report aims to elucidate the details of the electronic and lattice transport properties, thereby confirming that the higher thermoelectric (TE) performance of disordered polymorphs is essentially due to their complex crystallographic structures. In addition, we have presented synchrotron X-ray diffraction (SR-XRD) measurements and ab initio molecular dynamics (AIMD) simulations of the root-mean-square displacement (RMSD) in these materials, confirming anharmonicity and bond inhomogeneity for disordered polymorphs.
Keywords: Cu-based ternaries and quaternaries; thermoelectricity; Cu2ZnSnS4; Cu2ZnSnSe4; Cu2SnS3; mechanochemistry; order–disorder; X-ray diffraction; density function theory; ab-initio molecular dynamics; Raman spectroscopy

February 5, 2023

Thermoelectric performance in disordered Cu2ZnSnSe4 nanostructures driven by ultra-low thermal conductivity

Binayak Mukherjee, Eleonora Isotta, Marcelo Augusto Malagutti, Ketan Lohani, Luca Rebuffi, Carlo Fanciulli, Paolo Scardi

Abstract
High-energy reactive mechanical alloying (ball milling) was used to synthesize tetragonal and cubic polymorphs of Cu2ZnSnSe4. The ordered tetragonal (I-4) polymorph undergoes a phase transition above 400 K into a Cu-Zn disordered tetragonal (I-42 m) polymorph, while the cubic (F-43 m) polymorph with full cation disorder is stabilized at room temperature. Both polymorphs show ultra-low thermal conductivities, 0.42 W m−1 K−1 at 722 K and 0.21 W m−1 K−1 at 523 K for the disordered tetragonal and cubic phases respectively. The cubic polymorph has a higher zT in the low-temperature range, peaking at 0.26 (523 K), while the disordered tetragonal has a maximum zT of 0.46 at 712 K. The latter is the highest reported zT for stoichiometric Cu2ZnSnSe4, comparable to the best-performing doped materials in the literature. A combination of experimental results and ab-initio calculations point to a coupling between structural disorder and microstructure as the mechanism behind the reported performance.

Journal of Alloys and Compounds
Volume 933, 5 February 2023, 167756

https://doi.org/10.1016/j.jallcom.2022.167756