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High-pressure syntheses of TaS/sub 3/, NbS/sub 3/, TaSe/sub 3/, and NbSe/sub 3/ with NbSe/sub 3/-type crystal structure

Journal Article · · J. Solid State Chem.; (United States)
Transition metal trichalcogenides TaSe/sub 3/, TaSe/sub 3/, NbSe/sub 3/ and NbS/sub 3/ were prepared under the reaction conditions of 2 GPa, 700/sup 0/C, 30 min. NbSe/sub 3/ is exactly the same as that obtained in the usual sealed-tube method. The other products are modifications of each usual phase. They have crystal structures very similar to that of NbSe/sub 3/. The lattice parameters are a = 10.02 angstrom, b = 3.48 angstrom, c = 15.56 angstrom, ..beta.. = 109.6/sup 0/ for TaSe/sub 3/, a = 9.52 angstrom, b = 3.35 angstrom, c = 14.92 angstrom, ..beta.. = 110.0/sup 0/ for TaS/sub 3/, and a = 9.68 angstrom, b = 3.37, c = 14.83 angstrom, ..beta.. = 109.9/sup 0/ for NbS/sub 3/. In spite of the similarity in their crystal structures, these high-pressure phases show a variety of electrical transport properties. TaSe/sub 3/ is a superconductor having T/sub c/ at 1.9 K. TaSe/sub 3/ is a semiconductor with two transitions at 200 and 250 K. NbS/sub 3/ is a semiconductor with E/sub a/ = 180 MeV.
OSTI ID:
5227372
Journal Information:
J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 41:3; ISSN JSSCB
Country of Publication:
United States
Language:
English