Structural and superconducting properties of YBa₂(Cu_1-xAg_x)₃O₇ with x≤0.20

We have studied the structural and superconducting properties of the YBa₂(Cu_1-xAg_x)₃O₇ compounds with 0.0≤x≤0.20. The structure of the samples was determined by powder X-ray diffraction, thermogravimetric analysis, and infrared absorption spectra. These studies indicated that the Ag substituted replaced the Cu in the Cu-O chains in YBa₂Cu₃O₇, at least in the low concentration region (x≤0.05) where single-phased samples could be prepared. For x>0.05, impurity phases were detected in the X-ray diffraction patterns, which however, were so minor that they played no noticeable roles in the other physical properties measured. Field-cooled and zero-field-cooled magnetization measurements indicated that the substituted samples were homogeneous bulk superconductors with a large and constant ratio (≅43%) of the former to the latter throughout the range 0.0≤x≤0.14 measured. The superconducting transition temperature was determined resistively and was found to be suppressed at a relatively small rate of 0.08 K per Ag at % substituted.