Suppression of superconductivity in the (Er_1-x-yPr_xCa_y)Ba₂Cu₃O_{7- delta}(O<or=(x, y)<or= 0.3) system

Abstract

I Suppression of superconductivity in the (Er, --x -uPrxCay)Ba,Cu30, -( 0 4 (x, y ) 4 0.3) system R

Investigation of structure and transport properties of Gd1-x-zPrxCazBa2Cu3O7-δsystem

“…For Gd 1−z Ca z -123 samples, it is seen that both the lattice parameter a (in agreement with the ErCa-123 [7], YCa-123 [9] and Y 0.4 Pr 0.6 Ca x Ba 2−x Cu 3 O 7−δ [16] systems) and the in-plane Cu(2)-O(2) bond length (in agreement with [9]) increase with increasing z. The Cu(2)-O(2)-Cu(2) angle in CuO 2 planes also increases with increasing z.…”

“…It is then observed that the oxygen content in the CuO 2 planes (O(2), O(3)) is constant, and that it is more mobile at Cu-O chain (O(1), O(5)) layers. The variation of above-mentioned parameters is then followed, depending on the doping concentrations of Pr and Ca ions (table2).In table 2, the site occupations of Gd, Pr and Ca and the atomic positions of Cu(2), O(2), O(3) and O(4) in the lattice are given for GdPrCa-123 samples with various Pr and Ca ion concentrations.For Gd 1−z Ca z -123 samples, it is seen that both the lattice parameter a (in agreement with the ErCa-123[7], YCa-123[9] and Y 0.4 Pr 0.6 Ca x Ba 2−x Cu 3 O 7−δ[16] systems) and the in-plane Cu(2)-O(2) bond length (in agreement with[9]) increase with increasing z. The Cu(2)-O(2)-Cu(2) angle in CuO 2 planes also increases with increasing z.…”

“…Therefore, the interaction between the Pr and the O 2p magnetic moments decreases, resulting in the increase in T c [16]. On the other hand, for the cases of Er 1−y Ca y -123 [7], Y 1−y Ca y -123 [14], Y 0.4 Pr 0.6 Ca x Ba 2−x Cu 3 O 7−δ [16] and, fully oxygenated, (Y 1−x Ca x )(Ba 0.8 , Sr 0.2 ) 2 Cu 3 O z systems [10,12], the substitution of Ca decreases T c . These observations have been explained on the basis of effects such as over-doping, the dilution of the magnetic interaction, the pair breaking effect by Ca doping and the excess Ca acting as impurity phase.…”

“…of T c with Ca doping was first shown in Y 1−x−y Pr x Ca y -123 [3]. In compounds with oxygen deficiency, the substitution of Ca for R increases T c [4][5][6], but in samples which are annealed in oxygen it decreases T c [7][8][9][10][11][12][13]. In the tetragonal YBa 2 Cu 3 O 6 system partial Ca doping for Y causes the system to become a superconductor [6].…”

EFFECTS OF QUENCHING AND SINTERING TEMPERATURE ON ULTRASONIC ATTENUATION IN GdBaSrCu3O7−δ HIGH-Tc SUPERCONDUCTORS

“…Electrical resistance versus temperature measurements showed that the annealed samples are both superconducting with almost the same onset critical temperatures (T c onset) of 82 K. The quenched sample showed a semiconductor-like normal state behaviour with a T c omet of 55 K. Both the annealed samples were found to have optimum oxygen contents {8= 0) while for the quenched sample 5= 0.4 [4].…”