NORMAL-STATE TRANSPORT-PROPERTIES OF Y1-XPRXSRBACU3O7 AND Y1-XPRXSR2CU2.8RE0.2O7

In order to examine the effect of crystal chemistry on the T-c suppres sion behaviour of Pr in Y1-xPrxBa2Cu3O7, we have investigated in detai l the normal state transport properties - resistivity (rho) and thermo -electric power (TEP) - of two systems, (A) Y1-xPrxSrBaCu3O7 and (B) Y 1-xPrxSr2Cu2.8Re0.2O7. in case of the compound A, two kinds of samples were prepared - annealed in oxygen [O] and heated in argon followed b y oxygen annealing [AO]. As a result of the [AO] treatment, T-c could be increased by 5-14 K and superconductivity was induced in the sample x = 0.7. The [AO] treatment further reduced the rho(rt) and rho(0) po inting to a substantial reduction in scattering by defects (oxygen dis order). The room temperature value of the TEP (S-rt) revealed that the [AO] treatment increased the hole concentration in the CuO2 planes. I n case of compound B, for x = 0, the value of S-rt indicated that it w as underdoped. In spite of this, the effect of Pr was much less drasti c as shown by a smaller slope dT(c)/dx. Our S-rt data as a function of Pr concentration indicated that the hole depletion was retarded consi derably due to Sr substitution. To understand this slow charge transfe r of holes and the effect of [AO] treatment, one has to take into acco unt of the role played by Cu-O chains and oxygen defects in the basal plane. Our data support the model suggested by Fehrenbacher and Rice [ Phys. Rev. Lett. 70 (1993) 3471]. Further detailed microscopic experim ents and annealing procedures are needed to determine the role of the chains and how they affect the Pr(f) hybridization in the CuO2 planes. (C) 1998 Elsevier Science B.V.