Experimental data on the lattice parameter, thermoelectric power and microhardness of PbTe<In> crystals and the conversion from p- to n-type with increasing In content could be interpreted under the assumption that the In in PbTe<In> had variable valence: 2In2+ ↔ In+ + In3+. A crystal-quasi-chemical model was proposed for defect formation in PbTe<In>: the incorporation of In+ into octahedral interstices and In3+ into tetrahedral interstices of the close packing of Te atoms, accompanied by In2Te3 precipitation.

Charge State of Indium and Point Defects in Indium-Doped Lead Telluride Crystals. D.M.Freik, V.M.Boichuk, L.I.Mezhilovskaya: Inorganic Materials, 2004, 40[10], 1026-31