Syntheses, crystal structures, and physical properties of non-centrosymmetric MgIn2Te4 and MnIn2Te4

• Published in: Solid state sciences 2024-06, Vol.152, p.107552, Article 107552
• Main Authors: Shahid, Omair, Swati, Ishtiyak, Mohd, Rout, Sambit S.S., Ramanujachary, K.V., Niranjan, Manish K., Prakash, Jai
• Format: Article
• Language: English
• Subjects: Chalcogenides; Electronic structure; Single crystal; Thermoelectrics; X-ray diffraction
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2024.107552

In this study, we prepared two ternary tellurides, MgIn2Te4 and MnIn2Te4 (single crystals and bulk polycrystalline phases), by directly fusing the elements at high temperatures using the sealed tube synthesis method. Single crystal X-ray diffraction studies confirmed the non-centrosymmetric tetragonal structures (space group: I4‾ 2m) of the MgIn2Te4 and MnIn2Te4 phases with two formula units (Z = 2). Interestingly, the refined unit cell lengths of a = b = 6.2149(5) Å and c = 12.4240(19) Å for the MgIn2Te4 are slightly longer than those of the MnIn2Te4 structure (a = b = 6.1901(3) Å and c = 12.3877(7) Å). The asymmetric unit of these two MIn2Te4 (M = Mg and Mn) isostructural compounds contains three crystallographically independent sites: two disordered metal sites (M1/In1, M2/In2) and one Te1 site. Each metal atom in these structures is tetrahedrally coordinated with four Te1 atoms. Optical absorption studies for polycrystalline MgIn2Te4 and MnIn2Te4 samples showed bandgaps of 1.1(2) eV and 0.9(2) eV, respectively, consistent with these powders' black color. Seebeck studies confirm that holes are the majority of charge carriers for the MgIn2Te4 sample. The thermal conductivity (ktot) studies of the samples reveal ultralow values at 773 K: 0.37 Wm−1K−1 for the MgIn2Te4 and 0.44 Wm−1K−1 for the MnIn2Te4. Magnetic studies on the polycrystalline MnIn2Te4 show a paramagnetic behavior with a magnetic moment of 5.73 μB. Our theoretical studies indicate the possibility of achieving a high thermoelectric figure of merit (zT > 1.5) by optimizing the hole concentration in the MgIn2Te4 sample. [Display omitted] •Two ternary tellurides MgIn2Te4 and MnIn2Te4 were synthesized and characterized.•The optical absorption studies confirmed the semiconducting nature of both samples.•MgIn2Te4 and MnIn2Te4 exhibited ultra-low thermal conductivity values of 0.37 Wm−1K−1 and 0.44 Wm−1K−1 , respectively.•The MnIn2Te4 exhibited paramagnetic behavior with a magnetic moment of 5.73 μB.•The composite of MnIn2Te4/Sb2Te3 was also synthesized to improve the electrical conductivity.