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

Abstract

Three types of ternary selenides with layered composite crystal structures, (PbSe) 1.14 NbSe 2 [A], (PbSe) 1.14 (NbSe 2 ) 2 [B] and (PbSe) 1.14 (NbSe 2 ) 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 NbSe 2 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.