Surface-potential-controlled intergranular conductance in polycrystalline Bi2Te3 and Sb2Te3 thermoelectric materials: A comparative theoretical study
Year: 2026
Type: article
Abstract: Grain boundaries in polycrystalline Bi 2 Te 3 - and Sb 2 Te 3 -based thermoelectric materials may strongly modify charge transport through electrostatic band bending and space-charge-layer formation. In this work, surface-potential-controlled intergranular conductance is analyzed theoretically within the framework of classical semiconductor electrostatics and the grain-boundary barrier model. Calculations were performed at T = 300 K for p-type Bi 2 Te 3 and Sb 2 Te 3 using the dimensionless carrier-imbalance parameters ξ = 300 , 1000, and 3000 over the surface-potential interval − 15 ≤ Y s ≤ 25 . Both the absolute conductance variation | Δ G | and the signed conductance variation Δ G were evaluated. For negative surface potentials, Δ G > 0 because of hole accumulation near the grain boundary. Moderate positive surface potentials produce Δ G < 0 , corresponding to majority-carrier depletion. At larger positive Y s , the increasing electron contribution drives Δ G back toward positive values, producing a second zero crossing of the integrated conductance variation. Increasing ξ enhances the accumulation-side response, deepens the depletion minimum, and shifts this second zero crossing from Y s ≈ 13.7 for ξ = 300 to Y s ≈ 18.7 for ξ = 3000 . The dimensionless electrostatic part of the response has the same qualitative form for both materials under identical ξ and mobility-ratio conditions, whereas the dimensional amplitudes differ C = q μ p L i n i 2 through the material-dependent prefactor. The calculated values are 1.015 × 1 0 − 5 S for Bi 2 Te 3 and 5.297 × 1 0 − 6 S for Sb 2 Te 3 . Consequently, for the representative parameter sets considered here, the Bi 2 Te 3 conductance response is approximately 1.92 times larger than that of Sb 2 Te 3 . The results clarify the separate roles of surface potential, carrier imbalance, and material parameters in grain-boundary-controlled transport. The model is intended to describe qualitative electrostatic trends and does not constitute a direct calculation of the Seebeck coefficient, thermal conductivity, power factor, or thermoelectric figure of merit.
Source: Physics Open
Institution: Ferghana State University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,700
OpenAlex ID: W7206213830