Mat. Res. Bull., Vol. 22, pp. 943-949, 1987. Printed in the USA. 0025-5408/87 $3.00 + .00 Copyright (c) 1987 Pergamon Journals Ltd. NEW QUASI ONE-DIMENSIONAL AxNb6X 8 PHASES ISOSTRUCTURAL WITH Nb3Te 4 G. Huan and M. Greenblatt* Department of Chemistry Rutgers, The State University of New Jersey New Brunswick, NJ 08903 (Received March 12, 1987; Communicated by A. Wold) ABSTRACT A large number of new ternary niobium chalcogenides AxNb6X 8 with A = Na,K,Rb,Ca,Cu,Ag,ln,Zn,Cd,Sn,Pb and Bi, X = S,Te and A = Sn,Pb and Bi, for X = Se have been synthesized by molten salt ion exchange and/or ternary element insertion. TINb6X 8 with X = S,Te were prepared for the first time by high temperature methods. The A cations are incorporated into large empty channels of the three- dimensional network structure of Nb3X 4. The volume of the crystal lattice is nearly independent of the size of the cations. The extent of insertion (the value of x) appears to be limited primarily by electronic effects. MATERIALS INDEX: chalcogenides, tellurides, niobium Introduction Niobium chalcogenldes Nb3X 4 (X = S,Se and Te), discovered more than two decades ago (1,2), recently have been the subject of numerous investigations, because of their interesting structural and physical properties. The Nb3X 4 phases are isostructural, and form a three-dimenslonal (3D) network structure of edge and face sharing NbX 6 octahedra. The niobium atoms form zig-zag Nb-Nb chains running along the c direction (which is the needle axis); the intrachain Nb-Nb distances (~2.88A) are comparable to those in metallic Nb. The distance between niobium atoms in neighboring chains is considerably larger, suggesting quasi one-dimenslonal behavior. Another interesting feature of the Nb3X 4 structure is the presence of large hexagonal empty channels, also parallel with the c direction, providing a site for ternary element insertion in the lattice. Amberger et al (3) first reported on the superconducting properties of Nb3X 4 with critical temperatures (Tc) 4.0, 2.0 and 1.8K for X = S,Se and Te, respectively. *To whom correspondence should be addressed. 943