Effect of Substituting a Fraction of Cu by La on the Transport Properties of YBa<sub>2</sub>(Cu<sub>1−x</sub>La<sub>x</sub>)<sub>3</sub>O<sub>7−δ</sub> Superconductor (0 ≤ x ≤ 0.06)

Abstract

The effect of La doping on the transport properties and superconducting characterizations of YBa 2 Cu 3 O 7−δ was investigated. High quality YBa 2 (Cu 1−x La x) 3 O 7−δ superconductor was synthesized with La content of x = 0.00, 0.02, 0.04 and 0.06. The structure and surface morphology were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The best superconducting properties can be obtained for substitution of Cu by La concentration within a distinct range (x = 0.02, 0.04). The highest superconducting transition temperature T c (≈90 K), sharpest transition to superconductivity (ΔT = 5 K) and lowest electrical resistivity (ρ = 9.2 μΩ•cm) correspond to the composition with x = 0.02. Depression and degradation of the superconducting state as (x) increases to 0.06 were observed. Excess dopant of La (x = 0.06) results in a strong decoupling of chains and planes whereas optimal La doping (x = 0.02, x = 0.04) accumulates around the grain, beside the effect of hole filling within this range can adopt an alternate route to extensive oxygen anneal.