PHASE RELATION,CRYSTAL STRUCTURE AND SUPERCONDUCTIVITY IN Ba-La-Cu-O SYSTEM

Great efforts have been made to study the copper-containing oxide system since the discovery of superconductivity in Ba-La-Cu-O sestem was reported by Bednorz and Muller(1). In order to identify the reasons of superconductivity and explore new supurconductive material, it is crucial to determine the phase relations and crystal structures of the superducting compounds. The compound with Tc about 40K has been revealed to have the K2N1F4 type structure. The phase diagram of Ba-La-Cu-O system was studied by Che et al. in our laboratory,and another superconducting compound with Tc about 15K was discovered (2). The present study are concentrated on the superconductivity of the materials with nominal compositions La1−xBaxCuO3−y and the phase relation in this system.