The temperature dependences of the in-plane resistivity ab(T ) and out-of-plane resistivity c(T ) in Bi-2212 crystals covering the region from the underdoped to the overdoped regime have been measured. In the underdoped regime, ab(T ) deviates from a linear temperature dependence below a characteristic temperature T *, well above Tc, whose value decreases with increasing hole concentration. For underdoped crystals, ab(T) shows a typical S-shaped temperature dependence and ab = 0*+exp(-/T ) is satisfactorily obeyed over a much wider temperature range from slightly above Tc up to T *. Near the optimal region, the T -linear dependence of ab(T ) is maintained over a wide temperature interval. In contrast, a power law ab~Tn (n = 1.5-1.8) is followed in the overdoped regime. As regards the out-of-plane resistivity, on the other hand, c(T ) for the underdoped Bi2Sr2CaCu2Oy crystals shows a semiconductive behaviour, which is well described by the formula c = (C1/T)exp(C2/T ) + C3T + C4. The difference between the temperature dependences of c(T ) in the overdoped Bi2Sr2CaCu2Oy and Bi1.85Pb0.15Sr2CaCu2O8 + crystals, with basically the same values of Tc and nearly the same power-law temperature dependences of ab(T ) (ab~T 1.4), reveals that the inter-plane disorder in the form of oxygen vacancies and substituted cations acting as an extra blocking layer plays an important role in out-of-plane transport.

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Samples of stoichiometric composition La3Ca1−xSrxBa3Cu7Oy with 0≤x≤1.0 were prepared by the solid state reaction method. They were characterized by x-ray diffraction (XRD), resistivity, magnetization, and Raman measurements. Sr can replace up to 100% of Ca ions without the formation of any impurity phases, based on XRD measurements. Both the superconducting transition temperature Tc and the critical current density Jc(H) decrease monotonically with Sr content. The difference in ionic radius between Sr2+ and Ca2+ is believed to be responsible for the structural changes and suppression of superconductivity through the introduction of oxygen vacancies and disorder when Sr replaces Ca.