THE EFFECT OF THE SUBSTITUTION OF SM FOR BA ON THE SUPERCONDUCTOR SMBA2CU3OY

Characteristic changes occurring in SmBa2Cu3Oy superconductors an subs tituting Sm for Ba have been investigated, An appropriate amount of Sm substitution (0.05 less than or equal to 0.4, in the form of Sm1+xBa2 -xCu3Oy) promoted grain growth; the grain size became larger than that in the non-substituted sample and had a maximum value at x = 0.07; Si ngle-phase samples were obtained for 0 less than or equal to x less th an or equal to 0.8. The critical temperature increased by about 1.5K f or concentrations up to x = 0.02 while it decreased rapidly beyond thi s amount. Samples did not show superconductivity above 15 K for x grea ter than or equal to 0.4. The crystal structure transformed from ortho rhombic to tetragonal at x = 0.3. The average valency of the Cu and th e oxygen content decreased linearly with increase of x in the ranges o f 0 less than or equal to x less than or equal to 0.3 and 0.7 less tha n or equal to x less than or equal to 0.8, while they both increased l inearly for the range 0.3 less than or equal to x less than or equal t o 0.7.