Nanoscale stabilization of new phases in the PbTe-Sb2Te3 system: Pb(m)Sb(2n)Te(m+3n) nanocrystals

A series of novel rock-salt-type Pb(m)Sb(2n)Te(m+3n) nanocrystals (m = 2, 3, 4, 6, 8, and 10; n = 1 and 2) were successfully prepared using a colloidal synthesis route. These materials are stable only on the nanoscale and have no bulk analogues. Elemental compositions were determined using scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The nanocrystals exhibit well-defined band energies in the mid-IR region that are nearly independent of their atomic compositions. Pb(m)Sb(2n)Te(m+3n) nanocrystals behave as metastable homogeneous solid solutions at room temperature and tend to phase separate into the respective binary PbTe + Sb(2)Te(3) at 300 °C. Furthermore, pair distribution function (PDF) analysis suggests that the local structure of these Pb(m)Sb(2n)Te(m+3n) nanocrystals is distorted with respect to the rock-salt structure.