High Pressure Oxygen Treatment and the Substitution of Sr for Ba on (Nd1/3Ba2/3)2(Ce1/3Nd2/3)2Cu3Oy Superconductor

Substitution of Sr for Ba in the (Nd_1/3Ba_2/3)₂(Ce_1/3Nd_2/3)₂Cu₃O_y superconductor has been performed together with high pressure oxygen treatment, and the relationship among Sr content, lattice parameter, hole concentration and superconducting properties has been clarified. It has been found that there is a strong relationship between superconducting transition temperature (T_c) and c-axis length. The highest T_{c_{onset}} and T_{c_{zero}} of the (Nd_1/3(Ba_3/4Sr_1/4)_2/3)₂(Ce_1/3Nd_2/3)₂Cu₃O_y treated under 1300 atm oxygen pressure at 600°C for 24 hours are 59.3 K and 41.4 K, respectively. These transition temperatures are about 10 K higher than those of unsubstituted one.