Investigation of structure and transport properties of Gd_1-x-zPr_xCa_zBa₂Cu₃O_7-δsystem

Abstract

The granular Gd 1−x−z Pr x Ca z Ba 2 Cu 3 O 7−δ (GdPrCa-123) high-temperature cuprate superconductor samples were prepared and characterized. The electrical resistivity of Pr-free samples show a reduction in T c with increasing Ca content. For these samples, the T c (z) curve is nonlinear and a plateau appears at z ≈ 0.05-0.15. With increasing Ca concentration, the lattice parameter a increases. Moreover, it is observed that the in-plane Cu(2)-O(2) bond distance increases with increasing Ca content. On the other hand, the Cu(2)-O(2)-Cu(2) angle increases and the CuO 2 plane becomes flatter with successive Ca doping, which causes the suppression of superconductivity. The same bond distances in Pr-Ca substituted samples decrease slowly with increasing Ca doping, but increase with increasing Ca concentration after an optimum value. In addition, the electrical resistivity of Pr-Ca-doped samples shows an increase of T c with Ca doping up to an optimum value, whereafter it begins to decrease. We suggest that the competition of two effects, the number of holes and the flattening of CuO 2 planes by Ca doping, results in a nonlinear decrement in the T c (z) curve.

The Role of Ca in Superconducting and Magnetic Properties of Y1−x Ca x Ba2Cu3O7−δ (x=0.0–0.30)

“…The lattice parameters and other fitted parameters are given in Table 1. It can be seen from the XRD patterns and fitted lattice parameters, that with increase in Ca concentration, the orthorhombicity of the structure decreases, which is in agreement with early studies [2,5,8]. Cava et al [1] measured the lattice parameters with different oxygen stoichiometry for pure YBCO.…”

“…For oxygen deficient or partially oxygenated structure, the T c increases with increasing Ca concentration by enhancing the overall hole density [2,6,9]. In contrast, in oxygen rich samples Ca substitution causes reduction of T c [2,5,[7][8][10][11]. This T c depression is unlikely to be due to over-doping alone.…”

“…This results in increase of the lattice parameter a, and decrease in the orthorhombocity of the structure [6]. Whereas the Ca doping into the oxygen rich YBCO shows different behavior and it creates oxygen vacancies, increase in in-plane Cu(2)-O(2) bond distance, a parameter and the Cu(2)-O(2)-Cu(2) angle [7,8].…”

“…The detrimental behavior of T c in Ca substituted samples is due to the over-doping effect with disorder being created in superconducting CuO 2 planes [9][10][11]. In addition, Shakeripour et al [8] concluded that the reduction of T c with increasing Ca in oxygen rich system is due to the flattening of the CuO 2 planes. Therefore the induction of mobile carriers, overall oxygen content, oxygen disorder and structural changes are the factors which are responsible for T c behavior in Y 1-x Ca x BCO system.…”

EFFECT OF Pr AND Ca DOPING ON THE SUPERCONDUCTING PROPERTIES OF Dy1-2xPrxCaxBa2Cu3O7-δ HTSCs

“…For fixed Pr and Ca concentrations (fixed x and y), T c is linearly dependent on rare earth ion size. However, Shakeripour et al 19 reported that their R 1−x−y Pr x Ca y Ba 2 Cu 3 O 7 samples contained impurity phase for x > 0.15 and y > 0.25. The aim of this research is to contribute to an understanding of this problem with substitution at RE site and Ba site.…”