Influence of porosity on the critical currents of trifluoroacetate-MOD YBa2Cu3O7 films

The influence of porosity on the superconducting properties have been investigated on YBa2Cu3O7 thin films deposited on LaAlO3 (100) substrates by the so-called Trifluoroacetate (TFA) route. Micro-Raman spectroscopy have been used to determine the concentration of c-axis grains δ in different samples and their influence on the final film porosity as observed from SEM imaging. This has been compared with measurements of resistivity and critical currents in the same samples. We prove that this δ fraction is the main parameter controlling the porosity and hence the normal-state resistivity of the thin films. The optimization of the microstructure of these YBa2Cu3O7 TFA films allow to have high critical currents: Jc = 3 × 106 A/cm2 at 77 K