Different effects of Zn and Pr doping on YBa2Cu3O7-y

The substitution of Zn for Cu and Pr for Y in YBa2Cu3O7-y has been studied extensively, and got some meaningful results. Most attention was paid to the change of carrier concentration on superconductivity. In this work, high-resolution X-ray diffraction, including Phi-scan and rocking curves, was used to study some small size single crystals of Zn-and Pr-doped YBa2Cu3O7-y. It is discovered that the structural changes caused by the substitution of Zn for Cu mainly concentrate in the rock-salt block in the unit cell, i.e. the Cu(2)-O, Cu(1)-O, and Ba-O layers. But the structural changes caused by the substitution of Pr for Y distribute in the entire unit cell. Both the substitution of Zn and Pr decrease the value of T-c of YBa2Cu3O7-y. The effects of them were analyzed based on the structural change caused by substitutions. It is suggested that except the carrier concentration, structural change is an important factor to superconductivity. (C) 2002 Elsevier Science B.V. All rights reserved.