The systematic study of the normal-state transport properties of Bi-2212 crystals

The temperature dependences of the in-plane resistivity rho(ab)(T) and out- of-plane resistivity rho(c)(T) in Bi-2212 crystals covering the region from the underdoped to the overdoped regime have been measured. In the underdop ed regime, rho(ab)(T) deviates from a linear temperature dependence below a characteristic temperature T*, well above T,, whose value decreases with i ncreasing hole concentration. For underdoped crystals, rho(ab)(T) shows a t ypical S-shaped temperature dependence and rho(ab) = p(0)* + beta exp(-Delt a/T) is satisfactorily obeyed over a much wider temperature range from slig htly above T-c up to T*. Near the optimal region, the T-linear dependence o f rho(ab)(T) is maintained over a wide temperature interval. In contrast, a power law rho(ab) similar to T-n (n = 1.5-1.8) is followed in the overdope d regime. As regards the out-of-plane resistivity, on the other hand, rho(c )(T) for the underdoped Bi2Sr2CaCu2Oy crystals shows a semiconductive behav iour, which is well described by the formula rho(c) = (C-1/T) exp(C-2/T) C3T + C-4. The difference between the temperature dependences of rho(c)(T) in the overdoped Bi2Sr2CaCu2Oy and Bi1.85Pb0.15Sr2CaCu2O8+delta crystals. w ith basically the same values of T-c and nearly the same power-law temperat ure dependences of rho(ab)(T) (rho(ab) similar to T-1.4), reveals that the inter-plane disorder in the form of oxygen vacancies and substituted cation s acting as an extra blocking layer plays an important role in out-of-plane transport.