Mechanical and Transport Properties of Argon Annealed Y1 − x Ca x :123 Superconductors

Abstract

We report here the effects of argon heat treatment at 450 • C for 12 h on two similar sets of oxygenated Y 1 − x Ca x :123 superconducting samples prepared by two different heat treatments and oxygen purity as reported by Sedky and Abu-Ziad (Physica C 470, 659; 2010). The oxygenated samples are called ssqHp, sssHp, ssqLp, and sssLp, and the Ar annealed samples are called ssqHpAr, sssHpAr, ssqLpAr, and sssLpAr. It is found that the c parameter of annealed samples is gradually increased with Ca addition for all samples, while orthorhombic distortion (OD) is decreased. It is also noted that Ar heat treatment decreased the link between superconducting grains for all samples, and a linear decrease in microhardness (Vickers hardness number (VHN)) with Ca addition is obtained. But the rate of increase/decrease of the c parameter, OD, and VHN against Ca content is different in ssqHpAr and sssLpAr samples as compared to sssHpAr and ssqLpAr samples. Interestingly, the sssHpAr and ssqLpAr samples show a considerable loss of oxygen and small decrease in T c . While the ssqHpAr and sssLpAr samples show much smaller loss of oxygen and a gradual increase in T c up to 16 and 17 K, respectively. These A. Sedky results are discussed in terms of the mechanism of oxygen loss by Ca in addition to ssqHpAr and sssLpAr samples as compared to sssHpAr and ssqLpAr samples.