Full Experimental Seebeck Tensor Characterization for (p × n)-Type Transverse Thermoelectrics

(p × n)-Type transverse thermoelectrics are proposed as a potential thermoelectric material for waste heat harvesting. They can be made into single-leg devices, which can generate high voltage output from small temperature differences with adequate aspect ratios. Such materials are anisotropic, having an ambipolar Seebeck effect with a negative Seebeck coefficient along one direction and positive orthogonal Seebeck, generating a voltage drop perpendicular to an appropriately oriented temperature gradient, hence the name (p × n)-type. However, standard experiments only measured Seebeck coefficients along specific crystal axes, which is, in principle, insufficient to map the full Seebeck tensor of a low symmetry crystal. Here, we report results for an all-in-one measurement set-up for measuring the full Seebeck tensor on one sample with a custom-made apparatus. Experiments on pre-characterized isotropic material confirm this apparatus can accurately determine the 9 independent Seebeck components. Anisotropic van der Pauw measurements can also be integrated into the apparatus to measure the full in-plane anisotropic resistivity tensor on the same sample. Results of Seebeck tensor measurements in known anisotropic materials such as bismuth single crystals will be presented.