MICRO-STRAIN IN Y_(0.5)R_(0.5)Ba_2Cu_3O_(7-X) (R=Yb, Tm, Er, Ho, Dy, Gd, Eu, Sm, AND Nd)

摘要

Superconducting powders composed of 50:50 mixtures of yttrium and various rare-earth elements were analyzed by Rietveld analysis of x-ray diffraction data and magnetic susceptibility measurements. Crystallite size and micro-strain information obtained from the Rietveld analysis indicated that for mixtures containing Yb, Tm, and Er, crystallite sizes were significantly larger than for those containing larger rare-earths. Micro-strain minima were seen for the pure YBa_2Cu_3O_(7-X) control sample, as well as Y_(0.5)Eu_(0.5)Ba_2Cu_3O_(7-X) and Y_(0.5)Nd_(0.5)Ba_2Cu_3O_(7-X) The minimum for the control sample is due to the lack of Y-R mixing on the Y-site. The minima observed for the Eu and Nd-containing samples are explained by cation exchange between the Y-R and Ba-sites. Magnetic susceptibility hysteresis loops indicate that the Eu-containing sample exhibits better magnetic flux-pinning properties than the YBa_2Cu_2O_(7-X) control sample.