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.

Bi 2 Sr 2 Ca 1−x Pr x Cu 2 O y (x ranging from 0 to 0.5) single crystals have been grown by a self-flux method from Bi-rich melts. The crystals obtained manifest slim and plate-like shapes. The crystallinity is studied by x-ray diffraction. The x-ray θ-scanning rocking curve shows that the slim crystal has perfect crystal structure while the plate-like crystal is mosaic along the c-axis. The in-plane resistivity ρ ab (T ) has been measured for crystals with different Pr doping levels. T c is suppressed gradually upon doping while the residual resistivity increases strongly. A superconductor-insulator transition is observed which is attributed to the tetragonal-orthorhombic phase transition when the Pr content reaches about 0.5. The effect of oxygen doping on in-plane resistivity ρ ab (T ) is also studied for x = 0.22 and 0.40 crystals.