Effect of nickel and calcium substitution on the superconducting properties of the Y_1–xCa_x Ba₂Cu_3–yNi_y O_7–δ system with 0.1 ≤ x ≤ 0.3 and 0.0 ≤ y ≤ 0.2

Abstract

The effect of calcium (Ca) substitution in yttrium (Y) site and nickel (Ni) substitution in copper (Cu) site of Y_1–xCa_x Ba₂Cu_3–yNi_y O_7–δ (x = 0.1, 0.2, 0.3 and y = 0.0, 0.1, 0.2), materials prepared by solid state reaction method was investigated. Structural, average oxygen content and electrical resistivity measurements were studied using X-ray Diffraction (XRD), iodometric titration and four-probe method. From XRD analysis, all samples showed the orthorhombic symmetry of YBa₂Cu₃O_7–δ (YBCO). The average oxygen content δ increases with the substitution of Cu by Ni and Y by Ca. Such a phenomenon allows the appearance of oxygen vacancies in the samples. From the electrical resistivity results, critical temperature T_C decreases with the content of substitution y of Ni in Y_0.9 Ca_0.1Ba₂Cu_3–yNi_y O_7–δ system. In Y_0.9Ca_0.1Ba₂Cu_2.9Ni_0.1O_7–δ sample (y = 0.1), the variation ΔT_C falls only of 7% approximately, whereas a reduction in ΔT_C of 40% is observed in the YBa₂Cu_3–yNi_y O_{7 –δ} system. The critical temperatures T_C of the Y_1–xCa_x Ba₂Cu_2.9Ni_0.1O_{7 –δ} system (x = 0.1, 0.2 and 0.3) decreases with the content of substitution x of Ca until reaching a minimum at 67 K when x = 0.2, then it increases again.

GRAPHICAL ABSTRACT

KEYWORDS:

• Superconductor
• electrical properties
• crystallographic and critical temperature

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Funding

This work was supported by Direction Générale de la Recherche Scientifique et du Développement Technologique: [Grant Number 2020].