To clarify the behavior of thermally oxidized PbTe the phase equilibrium diagram was calculated taking into account the change of the standard Gibbs energies of formation with the temperature up to 873 K. The X-ray diffractometry (XRD) studies of thermally oxidized PbTe are, summarized. In good agreement with XRD studies the Pb-Te-O diagram predicts the formation of the lead tellurite PbTeO3 at the relatively low temperatures (<673 K). At higher temperatures (>673 K) it predicts the formation of other ternary PbTe oxides (Pb3TeO5, Pb5TeO7, and Pb2TeO4) detected in PbTe sintered material at high-temperature oxidation. This must be considered when choosing a method of preparing the nanostructured PbTe composites and when analyzing their properties. This should be considered when choosing processing techniques structured material. (C) 2014 Elsevier B.V. All rights reserved.