Carrier Concentration Dependence of Thermal Conductivity of Iodine-Doped n-Type PbTe

Abstract

Thermal conductivity (κ) of iodine doped n-type PbTe with carrier concentration (n) in the range of 1.5×10²⁴ to 3.4×10²⁵ m⁻³ was measured by using a laser flash method in the temperature range from 300 to 600 K. The scattering factor (r) was estimated from the temperature dependence of Hall mobility. The r values below 300 K changed from −0.43 to 0.39 with increasing electron concentration (n), while they were almost constant at −0.64 above 300 K. These results indicate that the scattering mechanism gradually changed from an ionized impurity scattering to the interaction between optical and acoustical phonon as the temperature (T) increased and n decreased. The κ values for all the samples showed the T⁻¹ dependence, the slope of which increased with increasing electron concentration in the measured temperature range. The lattice (κ_lattice) and carrier (κ_carrier) components of thermal conductivity were estimated using the observed κ and σ values on the basis of Fermi integration. The κ_carrier and κ_lattice values showed temperature dependence similar to that of the total κ value in the temperature range from 300 to 600 K. This fact suggests that the κ_lattice with electron concentration in the range of 1.5×10²⁴ to 3.4×10²⁵ m⁻³ is dominated by the Umklapp processes in the measured temperature range.