Superconducting and semiconducting properties of the Bi2Sr2Ca1−xGaxCu2Oy system

Abstract

X-ray-diffraction, electrical resistivity, and dc susceptibility measurements have been used to investigate the Bi2Sr2Ca1−xGaxCu2Oy system for different values of x in the range 0≤x≤1. There were no impurity phases detected from the diffraction patterns, which indicates that the Ga atoms are incorporated in the crystalline structure. The lattice parameter c of the orthorhombic cell decreases with increasing Ga concentration since the size of the Ga3+ ion is smaller than that of the Ca2+ ion it replaces. Samples with x≤0.6 are metallic and have a superconducting transition with a temperature of the midpoint of the transition that is independent of x for 0≤x≤0.6. There is a semiconducting behavior for 0.7≤x≤1.0. A thermally activated conduction process takes place in the low-temperature region of the samples with 0.7≤x≤0.9. In Bi2Sr2GaCu2Oy for which x=1.0 the thermally activated conduction process exists only for temperatures above 170 K. For lower temperatures the conduction is governed by a three-dimensional variable-range hopping process. The most probable jump distance and the average hopping energy at 10 K are 27 Å and 1 meV, respectively.

Source-reported materials — not catalogue approval

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