PREPARATION, CHARACTERIZATION AND INTERCALATION OF TERNARY CHALCOGENIDES WITH LAYERED COMPOSITE CRYSTAL-STRUCTURES FORMED IN THE BI-TA-S AND BI-TA-SE SYSTEMS

Two kinds of chalcogenides with layered composite crystal structures h ave been formed in Bi-Ta-S and Bi-Ta-Se systems depending on the prepa ration conditions: (BiS)(1.08)TaS2 and (BiS)(1.08)(TaS2)(2) for the fo rmer system and (BiSe)(1.09)TaSe2 and a new selenide (BiSe)(1.09)(TaSe 2)(2) for the latter. The new chalcogenide has been characterized by p owder X-ray diffraction and electron diffraction. The atomic coordinat es in the layer-stacking direction of the new chalcogenide and its hyd razine intercalation compound have been determined. The electrical res istivity measurement has suggested that all of these chalcogenides are low temperature superconductors.