Effect of Y substitution at Ca site on structural and superconducting properties of Bi:2212 superconductor

Structural, mechanical and superconducting properties of Bi2Sr2Ca1−xYxCu2Oy superconductors with various x values (0.00≤x≤0.50) are investigated by X-ray diffraction, scanning electron microscopy, Vickers hardness and resistivity measurements. It is found that the replacement of Ca2+ by Y3+ does not influence the phase purity of Bi:2212 while lattice parameters, orthorhombic distortion, surface morphology, oxygen content and hole carrier per Cu ion (P) are affected. Furthermore, the critical temperatures Tc are increased by increasing Y content up to 0.30, followed by a decrease with further increase of Y content up to 0.50. The values of Tc are 88, 94, 101, 104 and 50° K for x=0.00, 0.075, 0.15, 0.30 and 0.50, respectively. Similar behavior is obtained for the absolute values of true hardness Ht and surface energy γγ against Y content while the opposite behavior is recorded for the hole carrier per Cu ion (P), deduced from Tc values, against Y content. Similar behavior is obtained for the absolute values of true hardness Ht and surface energy γγ against Y content. These results are discussed in terms of possible reasons for suppression of superconductivity by Y substitution at the Ca site in the Bi:2212 superconducting system.