PACS 71.30.+h, 72.20.MyThe results of thermoelectric power (S) measurements of the lead chalcogenides PbS, PbSe, and PbTe at the initial NaCl-phase, as high-pressure semiconductors (above 2 -6 GPa), and at metal phases (above 10 -15 GPa) are presented. Phase transitions are discussed in terms of the model of Peierls distortion of lattice. IntroductionThe lead chalcogenides PbS, PbSe, and PbTe are narrow gap semiconductors with forbidden energy gaps of 0.286 eV, 0.16 eV, and 0.19 eV, respectively [1−3]. At high pressure P ∼ 2 −6 GPa these compounds undergo a phase transformation from the NaCl-to the GeS-type lattice [4−10] with about a two-fold increase of the lattice parameter a [5]. The resistivity of PbX (X is S, Se, or Te) compounds abruptly rises at the phase transition [4−8] similar to mercury chalcogenides, but contrary to most of other semiconductors. At pressures above ∼15 GPa further structural phase transitions were observed into the CsCl-type cubic lattice [9,10]. The jumps of the electrical resistance R during the first transitions [4−8] and the drop of R at the second one allows to suggest that structural changes are accomplished by electronic "semiconductor-metal" phase transitions [6,7,10]. Thermoelectric properties of new phases, which are capable to clarify the electronic structure [11], are unknown. The aim of the present work was the investigation of the thermoelectric power S of high pressure phases of PbX compounds.

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