We report here the effects of argon heat treatment
at 450 ◦C for 12 h on two similar sets of oxygenated
Y1 − xCax:123 superconducting samples prepared by two
different heat treatments and oxygen purity as reported bySedky and Abu-Ziad (Physica C 470, 659; 2010). The oxygenatedsamples 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 parameterof annealed samples is gradually increased with Ca additionfor 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 againstCa content is different in ssqHpAr and sssLpAr samples ascompared to sssHpAr and ssqLpAr samples. Interestingly,
the sssHpAr and ssqLpAr samples show a considerable loss of oxygen and small decrease in Tc. While the ssqHpAr and sssLpAr samples show much smaller loss of oxygen and a gradual increase in Tc up to 16 and 17 K, respectively. Theseresults 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.