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

Abstract

ESR, X-ray diffraction and resistivity measurements were carried out for as-sintered Ba₂Y₁Cu₃O_x, quenched Ba₂Y₁Cu₃O_xand as-sintered Ba₂Y₁Cu₃O_xF_y. 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 Ba₂Y₁Cu₃O_xF_ysuperconductor shows a strong ESR signal originating mainly from the impurity phase.