Calcium and oxygen doping in YBa_2Cu_3O_y

摘要

Both oxygen and calcium play important roles in inducing superconductivity in YBa_2Cu_3O_y (YBCO), which is an antiferromagnetic insulator at low O and Ca content. O induces superconductivity in Ca-free YBCO, while Ca does similarly in oxygen-deficient YBCO. For doping oxygen HgO was used as it decomposes at 476℃ into Hg, which escapes from the matrix leaving the crystal unaltered, and O, which provide a way to dope O in YBCO. Considering these facts, polycrystalline samples of Y_(1-x)Ca_xBa_2Cu_3O_y withx = 0, 0.1 and 0.2 with and without HgO addition were prepared through a solid-state reaction method. The samples were sintered at 950℃ in open atmosphere. These synthesized samples were characterized through using the X-ray diffraction technique (XRD) for phase evaluation, scanning electron microscopy (SEM) for grain morphology, energy dispersive X-ray analysis (EDX) for compositional analysis and the four-contact measurement technique for determining the superconducting transition temperature.