Synthesis, Superstructure, and Vacancy-Ordering in 2H-CuxTa1+ySe2 (x, y = 0.52, 0 and 0.16, 0.08)

摘要: Single crystals of CuxTa1+ySe2 were grown by chemical vapor transport. different compositions obtained at slightly reaction conditions from mixtures the reactants same nominal composition. It is suggested that diameters ampoules imply contributions convection and diffusion to mass transport, thus are responsible for ratios amount Cu, Ta, Se transported. 2H-Cu0.52TaSe2 (x = 0.52, y 0) formed in narrower ampoule (diameter 15 mm). The crystal structure based on MoS2 type stacking TaSe2 layers. Partial ordering Cu over tetrahedral sites a 2a0 × 2b0 × c0 superstructure with hexagonal Pm2 symmetry [a0 3.468 (1) A, c0 13.568 (3) A]. 2H-Cu0.16Ta1.08Se2 0.16, 0.08) wider 18 possesses NbS2-type stacking. A not formed, but presence intercalated Ta alternating van der Waals gaps reduction P63/mmc Pm1 3.439 (2) 12.870 towards hotter side up temperature 1168 K both reactions.