Three Types of Ternary Selenides with Layered Composite Crystal Structures Formed in the Pb-Nb-Se System

Three types of ternary selenides with layered composite crystal structures, (PbSe)1.14NbSe2[A], (PbSe)1.14(NbSe2)2[B] and (PbSe)1.14(NbSe2)3[C], have been prepared and characterized by powder X-ray diffraction, electron diffraction, intercalation and electric resistivity measurement. Results suggest that each selenide consists of PbSe layers(two-atoms-thick) and NbSe2 sandwiches(three-atoms-thick) stacked alternately with the ratios of 1:1 for A, 1:2 for B and 1:3 for C, respectively. Electric resistivity measurements suggest that B and C are superconductors whose transition temperatures are 3.4 K and 4.8 K, respectively.