Synthesis and characterization of superconducting YbBa2Cu3O7−δ and Y1−xLuxBa2Cu3O7−δ (0.0 < x < 0.75) : Lower limit of the rare-earth ion radius tolerated in the 123 cuprate system

Abstract

YbBa2Cu3O7−δ with a Tc (zero-resistance) of 89K has been prepared without contamination of Yb2BaCuO5. Monophasic LuBa2Cu3O7−δ cannot be prepared. Solid solutions of the type Y1 xLuxBa2Cu3O7−δ (0.0 < x ≤ slant 0.75) are, however, stable and superconducting (zeroresistance Tc, 89K). It appears that the lower limit of the rare earth ion radius tolerated by the 123 cuprate structure is close to that of Yb3+ (0.985 Å).