Improved Superconducting Properties of Thick YBa2Cu3O7−δ Film by Adding Amino-Rich Polyethyleneimine in Precursor Solution.

Polyethyleneimine (PEI) with an amount of -NH2 groups used in precursor solution could effectively reduce Cu2+ volatilization during the pyrolysis process. Thermogravimetric analysis shows that the temperature window of low-temperature pyrolysis for precursor solution with PEI (PEI-YBCO) is widened significantly. The slower pyrolysis process can enrich Cu2+ and improve critical current density (Jc) of PEI-YBCO films. The highest Jc is 3.03 MA/cm2 at 77 K when the amount of PEI is 0.5 g/10 mL and the film thickness is 400 nm. Then the thickness increases from 0.4 to 2.0 μm by changing the coating times. The Jc values of PEI-YBCO films decrease gradually with the thickness increase. However, the critical current (Ic) can be up to 197 A/cm (at 77 K, self-field) and Jc can still keep 1.68 MA/cm2 at 1.2 μm. [ABSTRACT FROM AUTHOR]