Origin of electrical contact resistance and its dominating effect on electrical conductivity in PbTe/CoSb3 composite

The electrical contact resistance (R-cont) is a crucial parameter that influences the electrical conductivity (sigma) in a composite material. Herein, we study the origin of Rcont and its effect on electrical properties of PbTe/CoSb3 composite. In particular, a series of (1-x)PbTe/(x)CoSb3 polycrystalline composite is prepared for x = 0.00, 0.25, 0.50, 0.75 and 1.00. The phase and chemical stability of the composites are investigated using X-ray diffraction and electron microscopy techniques. The Seebeck coefficient (S) and electrical conductivity (sigma) measured across a wide temperature range of 25-400 degrees C depict a degenerate semiconductor nature for all the samples. The sigma decreases from 3300 to 1000 S/cm with x and is attributed to a significant decrease in carrier mobility (mu) from 330 to 25 cm(2)/(s.V). For an in-depth investigation of the reduced a in the composite, R-cont between the phases is measured on PbTe/CoSb3 layered sample using the scanning thermoelectric microprobe (STM) technique (R-cont=14.1 mu Omega.cm(2)). Bruggeman asymmetrical model that considers R-cont further re-establishes the changes in a vs. x. A deeper understanding of the origin of R-cont is developed by preparing the band diagram for both phases using the Kelvin probe force microscopy (KPFM) technique, which suggests the presence of a potential barrier at the junction. The current-voltage (I-V) characteristic of the heterojunction indicates that the charge carrier follows the ohmic nature in one direction and non-ohmic in another. Hence, it indicates a possible scattering of carriers at the PbTe/CoSb3 interface in the composite that reduces mu. This study paves a new direction to select the composite components with aligned band structure that can be promising to design efficient TE composite materials.

Automated summary

This study investigates the influence of electrical contact resistance on the electrical properties of PbTe/CoSb3 composite. The presence of contact resistance leads to a decrease in carrier mobility and electrical conductivity. Additionally, the study explores the phase and chemical stability of the composites and prepares band diagrams to guide the design of efficient thermoelectric materials.