The introduction of artificial pinning sites in ${\text{YBa}}_2{\text{Cu}}_3{\text{O}}_{7-\delta }$ (YBCO) epitaxial thin films has been obtained by pulsed laser deposition (PLD) technique from YBCO-${\text{BaZrO}}_3$ (BZO) composite targets with BZO concentration ranging from 2.5 to $7\text{mol}\mathrm{\%}$ . The typical critical temperature, $T_c$ , drop observed in YBCO-secondary phase films grown by PLD has been successfully recovered by increasing the deposition temperature. Transport properties analyses revealed improved pinning force values for YBCO-BZO films for BZO concentration above $5\text{mol}\mathrm{\%}$ . These films exhibited an anomalous dual peak structure which has been ascribed to the presence of two pinning contributions. The crossover field, $B_m$ , separating these two pinning regimes has been observed to be temperature independent suggesting the occurrence of the matching field effect. The measured value of $B_m$ agreed with the matching field value, $B_{\Phi }=K{n}_d{\Phi }_0$ , as evaluated from transmission electron microscopy investigations. The mark of this phenomenon is retained down to 10 K, making YBCO-BZO more performing than pristine YBCO films at applied magnetic fields below $B_m$ in all the temperature range inspected. On the contrary, in the high magnetic field range (above $B_m$ ), the effectiveness of correlated pinning is progressively reduced on lowering the temperature suggesting that at low temperatures the dominant pinning contribution arises from isotropic pinning centers.

Pulsed laser deposited thin Y Ba₂Cu₃O_7−x (YBCO) films with pinning additions of 5 at. % Ba₂Y TaO₆ (BYTO) were compared to films with 2.5 at. % Ba₂Y TaO₆ + 2.5 at. % Ba₂Y NbO₆ (BYNTO) additions. Excellent magnetic flux-pinning at 77 K was obtained with remarkably high irreversibility fields greater than 10 T (YBCO-BYTO) and 11 T (YBCO-BYNTO), representing the highest ever achieved values in YBCO films.

Electrical and mechanical characterizations of YBCO coated conductors diffusion joints obtained in a 2 mm wide, Cu stabilizer free commercial tape provided by Superpower Inc. were reported. Two conductor pieces were overlapped for a length of 20 mm and kept in contact under a pressure as high as 80 MPa. A face-to-face approach was used, with or without an additional Ag tape insert. The joint was realized by Ag diffusion at a temperature of 200 and 400°C in N₂ and O₂ atmosphere, respectively. The resistivity of the joint was measured at 77 K in N₂ bath. The mechanical properties of the joint were characterized by means of single-lap tensile test operated at room temperature at a rate of 0.5 mm/min. The best results were obtained by high temperature joining in O₂ atmosphere. The resistivity of the joints was as low as 3.1 × 10^-12 ¿ m². This value is almost halved if an Ag insert is used. The mechanical properties of the joints are strongly dependent on the use of an Ag insert, since maximum load as high as 60 N can be applied if no additional insert is used. This value enhances to about 100 N when an Ag insert is employed. However, the joint obtained at low temperature in N₂ atmosphere is also interesting since the joint resistivity was slightly increased to 4.7 × 10^-12 ¿ m² and a maximum load as high as 50 N was obtained indicating that diffusion joints can be safely handled. These results are promising in perspective of oxygen free diffusion joints in Cu stabilized coated conductors.

A modified TFA-MOD method, using only barium trifluoroacetate, is presented. The yttrium and copper triflouroacetates were replaced by the alcoholic solutions of Cu and Y acetates dispersed in propionic acid. Fourier transformed infrared spectroscopy (FT-IR), thermal analyses (DTA/TG) coupled with mass spectrometry (MS) and X-ray diffraction analyses were used to study the decomposition of the precursor. The method permits the shortening of the pyrolysis time by a factor 4, with respect to conventional TFA-MOD method, due to the smaller amount of evolved hydrofluoric acid. Using this method 600 nm thick YBCO films were grown both on (100)SrTiO₃ and on CeO₂/YSZ/CeO₂/Pd buffered Ni-5at.%W substrates. The as obtained films exhibit good morphological, structural and superconducting properties with T_c (R=0) greater than 91K and with an out-of-plain texture of 0.24⁰ and 1.9⁰, respectively.

We have studied the critical current density $J_c$ for onset of vortex motion and the dynamic instability of the moving vortex lattice at high driving currents in superconducting (S)/ferromagnetic (F) $\mathrm{Nb}∕{\mathrm{Ni}}_{0.80}{\mathrm{Fe}}_{0.20}$ bilayers and in a single Nb film with the same thickness. The samples are all characterized by relatively high values of the pinning strength. The measured current-voltage characteristics are successfully described in the framework of the Larkin-Ovchinnikov model, modified in order to take into account the effect of the pinning close to the instability. We find that $J_c$ is smaller in the S/F bilayers than in the single film and argue that this is due to the strongly inhomogeneous order parameter in the bilayers. Also, the critical velocity $v^{*}$ for the occurrence of the instability is found to be significantly larger in the S/F bilayers than in the single S layer. By extracting the quasiparticle energy relaxation rate from $v^{*}$, we show that this effect is due to the same inhomogeneous order parameter and the resulting lower average value of the superconducting gap.