Zn migration during spark plasma sintering of thermoelectric Zn4Sb3

The phase homogeneity of spark plasma sintered thermoelectric Zn4Sb3 pellets along the pressing direction has been studied by potential Seebeck microprobe scanning and spatially resolved x-ray diffraction. Significant variations in the Seebeck coefficient reflect presence of different crystalline phases. The emergence of the ZnSb phase at the bottom of the pellet and metallic Zn impurity at the top explains the variation in the Seebeck coefficients. Quantitative phase distributions along the pressing axis were determined from the Rietveld refinements of spatially resolved x-ray diffraction patterns. These reveal a migration of highly mobilized Zn atoms under the direct current applied during spark plasma sintering. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731764]