Fast Preparation and Characterization of Quarternary Thermoelectric Clathrates

A large functionally graded single crystal has been synthesized by the Czochralski method. The resulting rod has a continuous composition range of Ba 8 Ga 16 (Si x Ge 1- x ) 30 going from x = 0.20(1) to 0.41(1). The exact composition was determined along the pulling direction by energy-dispersive X-ray spectroscopy (EDX), synchrotron powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD). Spatially resolved thermopower was measured using a Potential Seebeck Microprobe showing a gradual change in the thermopower with varying Si/Ge ratio. The gradual change is also observed in the clathrate lattice parameter. The present study demonstrates a method for fast preparation and characterization of a broad stoichiometry range in complex thermoelectric materials such as quarternary clathrate Ba 8 Ga 16 (Si x Ge 1− x ) 30 . Furthermore, the method can potentially be used to produce functionally graded materials, which have thermoelectric properties optimized over a broad temperature range.