Ln(3)T(2)N(6) (Ln = La, Ce, Pr; T = Ta, Nb), a new family of ternary nitrides isotypic to a high T-c cuprate superconductor

A new family of ternary nitrides Ln(3)T(2-x)N(6) (Ln= rare earth; T = Nb or Ta, 0 less than or equal to x less than or equal to 0.2) has been successf ully synthesized using Ga or Li3N as a flux. These compounds crystallize in the tetragonal space group I4/mmm (No. 139) with parameters a approximate to 4.05 Angstrom and c = 20.2 Angstrom. They are isostructural with the hig h T-c superconducting cuprate La2-xSrxCaCu2O6. Extended Huckel band structu re calculations show that the nitrides contain conducting TN2 layers simila r to the CuO2 layers. However, magnetic measurements performed on these ter nary nitrides do not show any superconducting transition down to 4 K. (C) 2 001 Academic Press.