Strong reduction of thermal conductivity in nanostructured PbTe prepared by matrix encapsulation

The preparation of nanometer sized inclusions of Sb, Bi, and InSb in bulk PbTe using a general liquid matrix encapsulation technique was investigated. It was found that the reduction in lattice thermal conductivity was not monotonic with increasing concentration of nanoparticles but there is an optimum concentration beyond which the lattice thermal conductivity increases. Higher concentrations formed larger particles due to nanoparticle fusion giving rise to micrometer-sized structures. The TEM revealed that the systems contain well-dispersed nanocrystals of Sb, Bi, and InSb respectively. The frequency and the size of these nanocrystals depended on concentration where higher concentration favored on average larger nanocrystals. The dependence of the lattice thermal conductivity of the PbTe-Sb system was studied as a function of Sb concentration. The results show that nanostructuring enhances acoustic phonon scattering in PbTe without the need to prepare solid solutions.