ICT2014 Abstracts

Thermoelectric materials that operate well below room temperature have potential application in space-based cooling systems. Many ytterbium-containing alloys and compounds exhibit an intermediate Yb valence behavior that gives rise to large Seebeck coefficients and power factors at low temperatures, rendering these materials potential candidates for this application. This research focuses on the intermediate valence compound YbCu₂Si₂ and its solid solutions with LaCu₂Si₂ and YbCu₂Ge₂. We show that by solid solution formation we are able to change the size of the unit cell and thereby tailor the average Yb valence via chemical relaxation and pressure. By altering the average Yb valence we can maximize the Seebeck coefficient as well as control the temperature at which the Seebeck coefficient peaks. Magnetic susceptibility measurements are used to determine the average Yb valence, and a strong correlation can be shown between this non-integer valence and the Seebeck coefficient.