Pressure induced quenching of planar rattling in Cu$_{10}$Zn$_{2}$Sb$_{4}$S$_{13}$ studied by specific-heat and x-ray diffraction measurements

TL;DR

This study investigates how pressure affects atomic rattling in two thermoelectric materials, revealing different pressure responses and mechanisms for Cu in CZSS and Ba in BGS through specific heat and x-ray diffraction analyses.

Contribution

It provides new insights into pressure-induced changes in rattling behavior and mechanisms in tetrahedrite and clathrate materials, highlighting the role of chemical pressure and atomic escape.

Findings

Rattling energy in CZSS decreases then increases with pressure

Rattling energy in BGS increases monotonically with pressure

Cu atoms escape from S3 triangle plane at high pressure in CZSS

Abstract

We have studied the pressure effect on the rattling of tetrahedrite Cu$_{10}$Zn$_{2}$Sb$_{4}$S$_{13\,}$(CZSS) and type-I clathrate Ba$_{8}$Ga$_{16}$Sn$_{30\,}$(BGS) by specific heat and x-ray diffraction measurements. By applying pressure $P$, the rattling energy for CZSS initially decreases and steeply increases for $P$ $\textgreater$ $1$ GPa. By contrast, the energy for BGS increases monotonically with $P$ up to 6.5 GPa. An analysis of the pressure dependent specific heat and x-ray diffraction indicates that the out-of-plane rattling of the Cu atoms in the S$_{3}$ triangle of CZSS originates from the chemical pressure, unlike the rattling of the Ba ions among off-center sites in an oversized cage of BGS. The rattling in CZSS ceases upon further increasing $P$ above 2 GPa, suggesting that Cu atoms escape away from the S$_{3}$ triangle plane.