Ln_3T_2N_6(Ln = La, Ce, Pr; T = Ta, Nb), a new family of ternary nitrides isotypic to a high T_c cupratesuperconductor

摘要

A new family of ternary nitrides Ln_3T_(2-x)N_6 (Ln = rate earth: T = Nb or Ta, 0 <= x <= 0.2) has been successfully synthesized using Ga or Li_3N as a flux. These compounds crystallize in the tetragonal space group 14/mmm (No. 139) with parameters a approx= 4.05 A and c = 20.2 A. They are isostructural with the high T_c superconducting cuprate La_(2-x)Sr_xCaCu_2O_6. Extended Huckel band structure calculations show that the nitrides contain conducting TN_2 layers similar to the CuO_2 layers. However, magnetic measurements performed on these ternary nitrides do not show any superconducting transition down to 4 K.