Evolution of low fluorine solution in decomposition and crystallization for YBa2Cu3Oy film growth

• A smooth surface is achieved at fast pyrolysis by using new low fluorine solution.
• The amount of corrosive fluorine-containing gas released can be greatly reduced.
• The nucleation of the low fluorine solution is still “ex situ BaF2” process.
• The YBCO film with a fast pyrolysis process shows high Jc (∼3.2 MA/cm2).

A new chemical solution deposition process for YBCO films based on a low fluorine content solution has been developed. The total content of fluorine in this solution is about 50% of that in all TFA solution, the amount of corrosive fluorine-containing gas released can be greatly reduced and the acute decomposition in a short time can be suppressed. A smooth and homogeneous surface have been achieved at the heating rate of 5 K/min by using this low fluorine solution. During the crystallization process, the composition of intermediated phases (BaYF, CuO) are changed with the annealing temperature. The reaction of nanocrystal Y2O3 and CuO is accompanied with the nucleation of YBCO phase, which indicates that there may be less second phase formation in the crystallization process. The traces of intermediate phase (BaYF–Ba(O,F)2) are observed. It demonstrates that the growth mechanism of the low fluorine solution is still “ex situ BaF2” process. The YBCO films with a fast pyrolysis process has been demonstrated high performance with Jc (77 K, self field) = ∼3.2 MA/cm2.