The Structure of α-Zn_4Sb_3: Ordering of the Phonon-Glass Thermoelectric Material β-Zn_4Sb_3

摘要

The β-modification of Zn_4Sb_3 is considered as a state-of-the-art thermoelectric material. The key to the high thermoelectric performance lies in the exceptional thermal conductivity, which is as low as that for glasslike materials. Although β-Zn_4Sb_3 was already discovered in the late 1960s and subsequently structurally characterized, the nature of its peculiar thermal conductivity behavior remained unknown. Very recently Snyder et al. and Cargoni et al. provided a plausible reason for this phenomenon when identifying a high degree of intricate disorder in the Zn substructure of β-Zn_4Sb_3. Structural disorder on the atomic level is one means to effectively damp heat-carrying phonons. Naturally, thermal conductivity is lowest in amorphous glasses, but on the other hand the low electron mobility inherent to glasses is not appropriate for a thermoelectric material. As a matter of fact, the ideal material is a "phonon glass—electron crystal" and β-Zn_4Sb_3 seems to fulfill these contradictory demands.