Synthesis and structure of layered compounds in the PbTe-Bi2Te3 and PbTe-Sb2Te3 systems

A number of tetradymite-like layered compounds in the PbTe-Bi2Te3 and PbTe-Sb2Te3 systems were prepared by a vertical Bridgman process, and their crystal structures were investigated by x-ray diffraction using single-crystal cleaved specimens. The atomic positional parameters and bond distances in PbBi4Te7 were determined. In the pseudobinary system PbTe-Sb2Te3, two new compounds were identified, PbSb2Te4 and PbSb4Te7, isostructural with PbBi2Te4 and PbBi4Te7, respectively. The positional parameters, site occupancies, and bond distances in the structure of PbSb2Te4 were determined. The room-temperature thermoelectric power of the grown ingots was measured along their length. All of the Sb compounds studied were found to be p-type, in contrast to the compounds of the PbTe-Bi2Te3 system.