Hall‐effect Measurements and Transport Properties of Heterostructures in the Model System NiTe₂‐Sn₁₂Sb₂Te₁₅

Abstract

In composite materials of NaCl‐type Sn12Sb2Te15 with x equivalents of CdI2‐type NiTe2 (x = 0.2; 1; 2), both phases are stable from room temperature up to 500 °C without a significant extent of mutual doping. The thermoelectric properties of this model system, complemented by Hall measurements, show clear trends with increasing x. Both electrical and thermal conductivities increase significantly whilst Seebeck coefficients decrease due to an increase in charge carrier concentrations. The overall Figure of merit zT is slightly impaired upon heterostructuring with NiTe2. However, the good reproducibility and cyclability of the measurements renders these composites an intriguing model system to qualitatively examine the applicability of a simple single parabolic band (SPB) model based on Hall‐effect data to rather metallic heterostructures. This model is best applicable to composites with lower fractions of NiTe2 and gives the direction for tuning the charge carrier concentrations toward the optimum upon heterostructuring. These findings are in accordance with B‐factor analysis and classical effective medium theory for spheroidal precipitates.