Measurements of the Room Temperature Thermoelectric Parameters of Lead Telluride†

Abstract

A modification of the technique suggested by Hérinckx and Monfils has been used to measure the room temperature thermoelectric parameters of single crystal n- and p-type lead telluride over a range of carrier concentrations. The Seebeck coefficient α, electrical conductivity σ (ohm⁻¹ cm⁻¹), and thermal conductivity K are related by the empirical equations : α_n = 717 -181 log σ_n μv//deg, 500 < σ_n < 6000, α_p= 702 - 187 log σ_pμv/deg, 200 < σ_p < 1700, K = 0.020 + 5× 10⁻⁶σ watt/cm/deg. n-type material has a maximum figure of merit at room temperature of 1-1 × 10⁻³ deg⁻¹ when σ_n= 750 and p-type of 1 ×10⁻³ deg⁻¹ when σ_n = 550. Comparison of the results with theory suggests that the charge carriers are scattered by the acoustical modes of vibration of the lattice and that the effective mass ratio is 0-25 for electrons and 0-35 for holes. Consistency between the theoretical calculations of Seebeck coefficient and thermal conductivity can be obtained if it is assumed that the lattice thermal conductivity is reduced by the addition of doping elements. A typical reduction is 20% for an addition of 0-2 atomic % of iodine atoms.