The effect of gallium substitution on the superconductivity of the BiSrCaCuO system

Abstract Magnetic susceptibility, X-ray diffraction and resistivity measurements of the system Bi 1.4 Pb 0.6 Sr 2 Ca 2− x Ga x Cu 3 O y are reported for 0 ⩽ x ⩽ 2. The high- T c 2223 phase with a T c of 107 K for x = 0 exists for x ⩽ 0.3. The low- T c 2212 phase with a T c of 75 K for x = 0 exists for the full range of x . The highest values of the critical temperature and the largest volume fraction of the low- T c phase in compounds with Ga occur for x = 0.5 ± 0.1. The identification of CaO by X-ray diffraction for x ⩾ 0.6 indicates that Ga replaces Ca in the compound.