Analysis of Local Structure about Zn in Zn doped Tetrahedrite using Extended X-ray Absorption Fine Structure (EXAFS) Spectroscopy*

Tetrahedrites are a class of naturally occurring minerals with high
thermoelectric efficiency. Thermoelectric materials are needed in devices
aiming to convert heat to electricity directly via the Seebeck effect, and
also for cooling without a refrigerant via the Peltier effect. We examine
pure Cu₁₂Sb₄S₁₃ and zinc doped Cu₁₀Zn₂Sb₄S₁₃ tetrahedrite to better
understand the metal to semiconductor transition at T~95K in the pure
tetrahedrite. Understanding why the transition is suppressed upon Zn doping
will shed light on the structural properties of this material. To probe the
crystal structure, X-ray spectroscopy data at the Zn and Cu K edges were
collected at the Stanford Synchrotron Radiation Lightsource (SSRL). We use
the Real Space X-ray Absorption Program (RSXAP) to analyze the Extended
X-ray Absorption Fine Structure (EXAFS) region for both the Zn and Cu
absorption edges. The analysis shows that the Zn edge data are more ordered
than the Cu edge data and that Zn substitutes on both the Cu1 and Cu2 sites.