Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric Materials
This study investigates the structural and mechanical properties of Cu–Se-based thermoelectric materials with varying Cu:Se stoichiometries (1.8, 1.9, and 2.0). Phase composition was examined using X-ray diffraction (XRD), revealing a transition from a mixed α/β-phase in Cu:Se = 2.0 to a fully cubic...
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2025-06-01
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| author | Fani Stergioudi Georgios Skordaris Maria Pappa Nikolaos Michailidis Vasileios Pavlidis Dimitrios Stathokostopoulos Aikaterini Teknetzi Lamprini Malletzidou George Vourlias Georgios Maliaris Ioanna K. Sfampa |
| author_facet | Fani Stergioudi Georgios Skordaris Maria Pappa Nikolaos Michailidis Vasileios Pavlidis Dimitrios Stathokostopoulos Aikaterini Teknetzi Lamprini Malletzidou George Vourlias Georgios Maliaris Ioanna K. Sfampa |
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| description | This study investigates the structural and mechanical properties of Cu–Se-based thermoelectric materials with varying Cu:Se stoichiometries (1.8, 1.9, and 2.0). Phase composition was examined using X-ray diffraction (XRD), revealing a transition from a mixed α/β-phase in Cu:Se = 2.0 to a fully cubic β-phase Cu<sub>2−x</sub>Se in Cu:Se = 1.8. Crystallite size analysis showed a reduction with increasing Cu content, which strongly influenced mechanical behavior. Vickers microhardness and nanoindentation tests were employed to assess hardness, elastic modulus, and elastic recovery. The Cu:Se = 2.0 sample exhibited the highest hardness but the lowest elastic recovery and elastic modulus from indentation, suggesting strong intragrain cohesion but limited elastic deformation due to fine grain structure. In contrast, the sub-stoichiometric Cu:Se = 1.8 phase displayed higher elastic modulus and recovery, possibly due to a more rigid Se sub-lattice and defect-mediated deformation mechanisms. Compression tests confirmed the higher bulk modulus in the Cu-deficient phase. Bending tests also showed that the Cu-deficient phase exhibited the highest bending modulus, further supporting its enhanced stiffness under elastic deformation. These results highlight the significant role of stoichiometry and crystallite structure in tuning the mechanical response of thermoelectric Cu–Se compounds, with implications for their durability and performance in practical applications. |
| format | Article |
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| issn | 2075-4701 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
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| series | Metals |
| spelling | doaj-art-d9261784f05e40a38f5d8d4ee372f8522025-06-25T14:10:53ZengMDPI AGMetals2075-47012025-06-0115664010.3390/met15060640Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric MaterialsFani Stergioudi0Georgios Skordaris1Maria Pappa2Nikolaos Michailidis3Vasileios Pavlidis4Dimitrios Stathokostopoulos5Aikaterini Teknetzi6Lamprini Malletzidou7George Vourlias8Georgios Maliaris9Ioanna K. Sfampa10Physical Metallurgy Laboratory, Department of Mechanical Engineering, School of Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreeceLaboratory for Machine Tools and Manufacturing Engineering, School of Mechanical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreecePhysical Metallurgy Laboratory, Department of Mechanical Engineering, School of Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreecePhysical Metallurgy Laboratory, Department of Mechanical Engineering, School of Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreeceLaboratory of Advanced Materials & Devices, School of Physics, Faculty of Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreeceLaboratory of Advanced Materials & Devices, School of Physics, Faculty of Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreeceLaboratory of Advanced Materials & Devices, School of Physics, Faculty of Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreeceLaboratory of Advanced Materials & Devices, School of Physics, Faculty of Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreeceLaboratory of Advanced Materials & Devices, School of Physics, Faculty of Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, GreeceHephaestus Laboratory, Department of Chemistry, School of Science, Democritus University of Thrace, 65404 Kavala, GreeceGroup R&D, KLEEMANN, Industrial Area of Kilkis, 61100 Kilkis, GreeceThis study investigates the structural and mechanical properties of Cu–Se-based thermoelectric materials with varying Cu:Se stoichiometries (1.8, 1.9, and 2.0). Phase composition was examined using X-ray diffraction (XRD), revealing a transition from a mixed α/β-phase in Cu:Se = 2.0 to a fully cubic β-phase Cu<sub>2−x</sub>Se in Cu:Se = 1.8. Crystallite size analysis showed a reduction with increasing Cu content, which strongly influenced mechanical behavior. Vickers microhardness and nanoindentation tests were employed to assess hardness, elastic modulus, and elastic recovery. The Cu:Se = 2.0 sample exhibited the highest hardness but the lowest elastic recovery and elastic modulus from indentation, suggesting strong intragrain cohesion but limited elastic deformation due to fine grain structure. In contrast, the sub-stoichiometric Cu:Se = 1.8 phase displayed higher elastic modulus and recovery, possibly due to a more rigid Se sub-lattice and defect-mediated deformation mechanisms. Compression tests confirmed the higher bulk modulus in the Cu-deficient phase. Bending tests also showed that the Cu-deficient phase exhibited the highest bending modulus, further supporting its enhanced stiffness under elastic deformation. These results highlight the significant role of stoichiometry and crystallite structure in tuning the mechanical response of thermoelectric Cu–Se compounds, with implications for their durability and performance in practical applications.https://www.mdpi.com/2075-4701/15/6/640copper selenidethermoelectric materialsmicrohardnessnanoindentationelastic modulusflexular modulus |
| spellingShingle | Fani Stergioudi Georgios Skordaris Maria Pappa Nikolaos Michailidis Vasileios Pavlidis Dimitrios Stathokostopoulos Aikaterini Teknetzi Lamprini Malletzidou George Vourlias Georgios Maliaris Ioanna K. Sfampa Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric Materials Metals copper selenide thermoelectric materials microhardness nanoindentation elastic modulus flexular modulus |
| title | Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric Materials |
| title_full | Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric Materials |
| title_fullStr | Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric Materials |
| title_full_unstemmed | Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric Materials |
| title_short | Influence of Copper Stoichiometric Composition and Compaction Method on Mechanical Properties of Cu<sub>x</sub>Se Thermoelectric Materials |
| title_sort | influence of copper stoichiometric composition and compaction method on mechanical properties of cu sub x sub se thermoelectric materials |
| topic | copper selenide thermoelectric materials microhardness nanoindentation elastic modulus flexular modulus |
| url | https://www.mdpi.com/2075-4701/15/6/640 |
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