Rapid synthesis and enhanced thermoelectric properties of Ba8Cu6Ge8xSi40-8x (x = 0, 1, 2, 3) alloys prepared using high-temperature, high-pressure method

Clathrate compounds of Ba8Cu6Ge8xSi40-8x (x = 0, 1, 2, 3) were synthesized using a high-temperature, high-pressure (HPHT) method. The study explored chemical doping with Ge at the Si site to optimize the thermoelectric figure of merit in a series of Ba8Cu6Ge8xSi40-8x alloys. The synthesis time was significantly reduced from a few days to 30 min, and the electrical resistivities, Seebeck coefficients and thermal conductivities of the samples were measured in the temperature range of 303-773 K. Among all of the samples, the sample with x = 3 showed the lowest thermal conductivity of 0.91 W m-1 K-1 at 573 K and the maximum the dimensionless figure of merit (ZT) value of 0.42 at 673 K. Combining elemental substitution and HPHT effectively improved the thermoelectric properties of clathrates. © 2016 Elsevier B.V. All rights reserved.