Enhancing the Thermoelectric Performance of GeSb(4)Te(7) Compounds via Alloying Se.

Ge-Sb-Te compounds (GST), the well-known phase-change materials, are considered to be promising thermoelectric (TE) materials due to their decent thermoelectric performance. While Ge(2)Sb(2)Te(5) and GeSb(2)Te(4) have been extensively studied, the TE performance of GeSb(4)Te(7) has not been well explored. Reducing the excessive carrier concentration is crucial to improving TE performance for GeSb(4)Te(7). In this work, we synthesize a series of Se-alloyed GeSb(4)Te(7) compounds and systematically investigate their structures and transport properties. Raman analysis reveals that Se alloying introduces a new vibrational mode of GeSe(2), enhancing the interatomic interaction forces within the layers and leading to the reduction of carrier concentration. Additionally, Se alloying also increases the effective mass and thus improves the Seebeck coefficient of GeSb(4)Te(7). The decrease in carrier concentration reduces the carrier thermal conductivity, depressing the total thermal conductivity. Finally, a maximum zT value of 0.77 and an average zT value of 0.48 (300-750 K) have been obtained in GeSb(4)Te(5.5)Se(1.5). This work investigates the Raman vibration modes and the TE performance in Se-alloyed GeSb(4)Te(7) sheddinglight on the performance optimization of other GST materials.