STABILIZATION OF THE 108 K SUPERCONDUCTING PHASE IN THE BI0.7PB0.3SRCACU1.8OY SYSTEM

Samples having the nominal composition Bio.7Pbo.3SrCaCul8Oy were prepared by a solid-state reaction and characterized by energy-dispersivex-ray microanaly- sis, resistivity measurements, and magnetically modulated microwave absorption (MAMMA). Longer annealing times resulted in more homogeneous samples having a single superconducting transition to zero resistance at 108 and 105 K at 0.1 and 1 mA, respectively. The MAMMA measurements clearly show differ- ences in sample homogeneity with different annealing times.