Syntheses of a series of BaCuAgSe ( = 0 - 1.0) selenides and evaluation of their thermoelectric properties

• Published in: New journal of chemistry Vol. 48; no. 24; pp. 11129 - 11139
• Main Authors: Swati, Yadav, Sweta, Shahid, Omair, Prakash, Jai
• Format: Journal Article
• Published: 17.06.2024
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d4nj00989d

The development of new sulfide and selenide-based thermoelectric (TE) materials is critical for the mass production of TE devices due to the higher earth abundance of S/Se than Te. In this work, we have prepared single crystals of Ag-substituted BaCu 2− x Ag x Se 2 ( x = 0 - 0.8) by direct fusion of elements at high temperatures. As characterized by single crystal X-ray diffraction (SCXRD) studies, each of the structures (space group: Pnma ) contains two transition metal sites (M1 and M2), and the Ag atoms are disordered with Cu atoms at both sites with a slight preference for the M2 site. Phase pure polycrystalline BaCu 2− x Ag x Se 2 ( x = 0 - 1.0) samples have also been synthesized, which are semiconductors as confirmed by optical absorption and resistivity studies. All these samples show positive values of the Seebeck coefficient, suggesting the p-type electrical conduction. Our thermal conductivity ( k tot ) studies demonstrate a remarkable drop in k tot values on increasing the Ag-substitution in the BaCu 2− x Ag x Se 2 phases with the lowest k tot value of 0.33 W m −1 K −1 (673 K) for the x = 1.0 sample. Our studies show the potential of the BaCuAgSe 2 for TE applications with higher z T values if the hole concentration of the phase can be fully optimized. Single crystals and phase pure polycrystalline BaCu 2− x Ag x Se 2 samples have been synthesized to study the effect of Ag substitution on their structural parameters and physical properties.