Off-stoichiometry effect on thermoelectric properties of the new p-type sulfides compounds Cu2CoGeS4

• Published in: Journal of alloys and compounds Vol. 826; p. 154240
• Main Authors: Bourgès, Cédric, Al Rahal Al Orabi, Rabih, Miyazaki, Yuzuru
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-06-2020; Elsevier BV
• Subjects: Carrier density; Cu2CoGeS4; DFT; Elastic properties; Electrical resistivity; Seebeck effect; Spark plasma sintering; Stoichiometry; Sulfide; Thermal conductivity; Thermal stability; Thermoelectric; Thermoelectricity; Transport properties; Sulfide; Spark plasma sintering; Thermoelectric; DFT; Cu2CoGeS4
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.154240

An in-depth analysis of Cu2+xCo1-xGeS4 (CCGS) has been performed to illustrate its potential as a new p-type compound for thermoelectric (TE) applications with suitable thermal stability. An intrinsic semiconductor behavior is reported with attractive TE properties, characterized by a large Seebeck coefficient and intrinsic low thermal conductivity. Band structures and elastic properties calculations sustained the experimental observations and revealed the dominant role of Cu/Co ratio in electrical transport properties. A promising TE performance is achieved through a carrier concentration tuning by Cu/Co ratio control, with a zT = 0.37 at 725 K resulting from combined large PF enhancement and a reduced κ.
•We performed the band structure and elastic properties calculations of Cu2CoGeS4 compound.•We synthesized the Cu2+xCo1-xGeS4 (0 = x ≤ 0.225) bulk compounds series by sealed tube reaction and Spark Plasma Sintering.•We studied the structural and thermal stability of the compounds above 775 K.•The thermoelectric properties were reported and optimized up to zT = 0.37 at 725 K.•The effect of the Cu/Co ratio in the transport properties was highlighted.