Síntese, microestrutura e comportamento magnético do supercondutor CaLaBaCu3Oy

Abstract

Copper-based superconductors, such as CaLaBaCu3Oy (CLBC), continue to be widely investigated due to the complexity of their structures, the variety of physical properties they exhibit, and their potential in technological applications. In this work, we conducted an experimental investigation of the structural and magnetic properties of CLBC. For this, two polycrystalline samples were prepared by solid-state reaction sintering: sample 1, with composition CaLaBaCu3Oy, and sample 2, with composition Ca0.5La1.25Ba1.25Cu3Oy. The structural characterization of the samples was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The analysis of the results obtained through SEM revealed characteristics typical of sintered materials, with the presence of small grains, irregular shapes, and random orientations. The identification and quantification of crystalline phases and the determination of lattice parameters were performed through the Rietveld refinement method. Sample 1 revealed a tetragonal structure, without impurity phases, in agreement with the experimental data reported in the literature. On the other hand, sample 2 showed, in addition to the tetragonal phase, peaks corresponding to CaO, which crystallizes in a cubic structure. Furthermore, magnetization measurements were carried out using zero-field cooling (ZFC) and f ield-cooled cooling (FCC) procedures, with magnetic fields applied between 0.010 kOe and 20 kOe, on a CaLaBaCu3Oy sample. The results indicated that the behavior of the magnetic irreversibility line (LIM) of the material is similar to that observed in other granular compounds. The MIL was described by the superconducting glass model, following a power law of the Almeida-Thouless (AT) type in low fields and a Gabay-Toulouse (GT) type power law in higher fields. This analysis revealed a transition from the AT regime to the GT regime at fields above H = 1 kOe. The su perconducting transition of CaLaBaCu3Oy, determined from magnetic measurements, exhibited a critical temperature of 79.12 K.