Superconductivity in Perovskite Ba 0.85− x La x Pr 0.15 (Bi 0.20 Pb 0.80 )O 3− δ

The perovskites Ba 0.85− x La x Pr 0.15 (Bi 0.20 Pb 0.80 )O 3− δ (0.0 ≤ x ≤ 0.07) have been synthesized by traditional solid-state method. They crystallize in P1 space group confirmed by x-ray and rotational electron diffraction data. X-ray photoelectron spectroscopy data indicate that the valences of bismuth are + 3 and + 5, while the valences of lead are + 2 and + 4 in this solid solution. They all show superconductivity. The T_c^zero (the highest temperature at which the sample shows zero electrical resistivity) decreases with an increase of La in the sample.