Hall emf and conductivity of the superconducting oxide system BaPbO3--BaBiO3

Measurements were made of the Hall emf (at room temperature) and of the conductivity (in the range 2.5--300 0K) of superconducting ceramics BaPb/sub 1-times/Bi/sub x/O3 with compositions corresponding to x = 0, 0.05, 0.13, 0.2, 0.3, 0.4, and 0.5. The conduction electron density n was calculated and the dependence T/sub c/ (n) was derived. A correlation was found between T/sub c/ and n for samples with different Bi concentrations. The low-temperature conduction in the samples with x = 0.3, 0.4, and 0.5 was found to be activated and the activation energies of these samples were found. The activated conduction in the sample with x = 0.3 was characterized by an energy epsilon-c3 and was observed down to the superconducting transition temperature. It was found that epsilon-c3<Δ, where Δ is the superconducting energy gap in the quasiparticle spectrum. An analysis was made of possible reasons for the reduction in the diamagnetic response of the superconducting samples as a result of a reduction in size of the component grains