On the possibility of the removal of charge localization by reduced disorder level in Nd1−xCaxBa2Cu3Oy

We have synthesized and characterized underdoped Nd1−xCaxBa2Cu3Oy (NCBCO) (x=0, 0.1, 0.3 and 0.5). The variation of resistivity with temperature has been analyzed. With the increase in the concentration of Ca (x) the normal state transport behavior is found to be very sensitive. The normal state resistivity in NCBCO with x=0.5 is metallic even if the undoped (x=0) sample is a nonmetallic one. The underlying mechanism of the transformation of the normal state may be associated with both the intergranular and intragranular networks. The separation between two superconducting layers remains unaltered and so the global nature of granularity in all NCBCO. However, the dominating role in the transformation of the normal state resistivity may be caused by the possible reduction of the disorder level in CuO2 planes.