ESR and X-Ray Diffraction Studies on Ba-Y-Cu-O Superconductors

ESR, X-ray diffraction and resistivity measurements were carried out for as-sintered Ba2Y1Cu3Ox, quenched Ba2Y1Cu3Oxand as-sintered Ba2Y1Cu3OxFy. The ESR spin density is found to be a good measure for the amount of an impurity phase Ba1Y2Cu1O5. A decrease in the sintering temperature reduces the amount of the impurity phase. A transition from a superconducting orthorhombic to a nonsuperconducting tetragonal structure induces no large change in the ESR signal. It is also found that an as-sintered Ba2Y1Cu3OxFysuperconductor shows a strong ESR signal originating mainly from the impurity phase.