Contamination of YBCO bulk superconductors by samarium and ytterbium

• YBCO bulk single-grain superconductors with Y2O3 and CeO2 addition were prepared by the TSMG process.
• WDS analyses confirmed the presence of 0.1 wt% Sm and 0.25 wt% Yb in the prepared samples.
• The influence of Sm and Yb contamination on superconducting properties is shown.
• Different experiments were realized in order to decrease the pollution of prepared samples.

Y–Ba–Cu–O (YBCO, Y-123) single-grain bulk superconductors with a nominal composition Y1.5Ba2Cu3Ox and 1 wt% CeO2 addition were prepared by the optimized Top-Seeded Melt-Growth process. Small single-crystalline pieces cut from the SmBa2Cu3Oy (Sm-123) bulk were used for seeding of epitaxial growth. Wavelength-dispersive spectrometry (WDS) confirmed that prepared samples contain besides samarium from the seed also ytterbium from the substrate. The influence of maximum melting temperature, Tmax and dwell time on the contamination of the bulk samples was studied. Y2BaCuO5 (Y-211) barriers against samarium diffusion from the seed to melted sample were tested. Using a NdBa2Cu3Oz (Nd-123) seed and a combination of Y2O3 and Yb2O3 substrate led to a high critical temperature (Tc(50%) = 91.54 K) of prepared sample.