We present some results of a.c. susceptibility measured on pure and doped with indium and potassium Bi-compounds. For both the 80K and 110K phases, we follow the χ′ and χ″ variations as a function of (a) the annealing treatment, (b) the Sr/Ca ratio and (c) the doping. Indium doping has either a positive or a negative effect on the 80K material, depending on the Sr/Ca ratio. It induces an important increase of the superconductive volume of the 110K material. Effects due to potassium are opposite. The experimental results agree with the fact thatTc goes through a maximum as the hole density increases.
Volume 43, 2020
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