Growth and characterization of REBa_2Cu_3O_(7-δ) superconductor single crystals obtained from xenotime mineral

摘要

Single crystals of REBa_2Cu_3O_(7-δ) (RE=natural mixture of Yand heavy lanthanides in the single crystals) superconductor were successfully grown using rare-earth oxides extracted from xenotime mineral, allowing an alternative and simple route for superconductor single-crystal production. The methodology to extract the rare-earth mixed oxides from the xenotime mineral has three main steps: alkaline fusion, acid lixiviation and oxalic precipitation. Large single crystals with a typical 5 × 5 × 0.03 mm~3 size were obtained by using a CuO-BaO self-flux and were characterized by scanning electron microscopy (SEM), energy-dispersive electron spectroscopy, X-ray diffraction, magnetic measurements and nanoindentation. The composition of the rare-earth elements of the crystal was different from the starting mixture, possibly due to the different solubilities of the elements in the melt. The final crystal stoichiometry was RE:Ba:Cu=1 :2:3. X-ray diffraction analysis showed highly oriented c-axis (c=11.716±0.002 A). The critical temperature was determined to be around T_C≌88-89K after the crystals have been submitted to oxygen annealing. Hardness and elastic modulus for ab- and b(a)c-planes were 8.5 ± 0.5 and 160 ± 20GPa, respectively.