X-ray and electrical studies of the phase transition in Pb_1-xGe_xSe

Electrical measurements on single-crystal samples of Pb_1-xGe_xSe with x=0.02-0.08 showed anomalous scattering of carriers indicating a second-order phase transition in these crystals. The dependence of the transition temperature on the crystal composition was established. X-ray studies showed a rhombohedral distortion of the cubic lattice below T_c; the temperature dependence of the rhombohedral angle was determined. Thallium impurity was found to lower the transition temperature markedly. The causes of the regular decrease in T_c of lead germanium chalcogenide solid solutions under the substitution Te->Se->S are discussed.

Keywords: lead germanium selenide solid solution, IV-VI narrow-gap semiconductors, ferroelectric phase transition, Curie temperature