The series of Pb9.6Sb0.2Te10-xSe x compounds with different Se content (x) were prepared, and their structure was investigated at the atomic and nanosized regime level. Thermoelectric properties were measured in the temperature range from 300 to 700 K. The Pb9.6Sb0.2Te10-xSex series was designed after the refinement of the single-crystal structure of Pb 3.82Sb0.12Te4 (Pb9.6Sb 0.3Te10; S.G. Pm3̄m) by substituting isoelectronically in anion positions Te by Se. The Pb9.6Sb 0.2Te10-xSex compounds show significantly lower lattice thermal conductivity (κL) compared to the well-known PbTe1-xSex solid solutions. For Pb9.6Sb 0.2Te3Se7 (x = 7), a κL value as low as 0.40 W/m-K was determined at 700 K. High-resolution transmission electron microscopy of several Pb9.6Sb0.2Te 10-xSex samples showed widely distributed Sb-rich nanocrystals in the samples which is the key feature for the strong reduction of the lattice thermal conductivity. The reduction of κL results in a significantly enhanced thermoelectric figure of merit of Pb 9.6Sb0.2Te10-xSex compared to the corresponding PbTe1-xSex solid solution alloys. For Pb9.6Sb0.2Te3Se7 (x= 7), a maximum figure of merit of ZT ≈ 1.2 was obtained at ∼650 K. This value is about 50% higher than that of the state-of-the-art n-type PbTe. The work provides experimental validation of the theoretical concept that embedded nanocrystals can promote strong scattering of acoustic phonons.
ASJC Scopus subject areas
- Colloid and Surface Chemistry