Novel superconductors obtained by electrochemical Zn intercalation of beta-ZrNCl and related compounds

We present results of an electrochemical intercalation study of Zn into bet a -ZrNCl, beta -ZrNBr and beta -HfNCl. For beta -ZrNCl an intercalation rea ction takes place, leading to the final compound Zn0.04ZrNCl with a superco nducting transition temperature T-c of 15 K. A similar behaviour is observe d for beta -ZrNBr where the insertion reaction produces the superconducting compound Zn0.04ZrNBr with a T-c of 14 K, whereas attempts to obtain ZnxHfN Cl superconductors applying the same conditions failed. In comparison to be ta -MNX compounds with monovalent inserted ions, superconductivity in Zn do ped beta -MNX occurs at much lower levels of electron doping, although the values of T-c are similar. (C) 2000 Elsevier Science Ltd. All rights reserv ed.