The influence of twin boundaries on the Flux Line Lattice structure in YBaCuO: a study by Small Angle Neutron Scattering

The influence of Twin Boundaries (TB) on the Flux Line Lattice(FLL) structure was investigated by Small Angle Neutron Scattering (SANS). YBaCuO single crystals possessing different TB densities were studied. The SANS experiments show that the TB strongly modify the structure of the FLL. The flux lines meander as soon as the magnetic field makes an angle with the TB direction. According to the value of this angle but also to the ratio of the flux lines density over the TB density, one observes that the FLL exhibits two different unit cells in the plane perpendicular to the magnetic field. One is the classical hexagonal and anisotropic cell while the other is affected by an additional deformation induced by the TB. We discuss a possible relation between this deformation and the increase of the critical current usually observed in heavily twinned samples.Comment: accepted for publication in Phys Rev

The influence of twin boundaries on the Flux Line Lattice structure in YBaCuO: a study by Small Angle Neutron Scattering

The influence of Twin Boundaries (TB) on the Flux Line Lattice(FLL) structure was investigated by Small Angle Neutron Scattering (SANS). YBaCuO single crystals possessing different TB densities were studied. The SANS experiments show that the TB strongly modify the structure of the FLL. The flux lines meander as soon as the magnetic field makes an angle with the TB direction. According to the value of this angle but also to the ratio of the flux lines density over the TB density, one observes that the FLL exhibits two different unit cells in the plane perpendicular to the magnetic field. One is the classical hexagonal and anisotropic cell while the other is affected by an additional deformation induced by the TB. We discuss a possible relation between this deformation and the increase of the critical current usually observed in heavily twinned samples

Routes to obtain high performance, high Tc superconducting bulk materials

International audienceThis paper reviews our investigations for understanding the fundamental relations between physical properties, crystal chemistry, phases relation and processings on the compounds YBa2Cu3O7−x and Bi(Pb)2Sr2Ca2Cu3O10+x. These two systems have in common the complexity of their crystal structure and multi-components chemistry which require challenging material processing for applications. In the YBaCuO system, horizontal bridgman and melting zone processes have demonstrated the possibility of obtaining high performances in this system, with different shaping. A high reproducibility with low material losses have been achieved with a top seeding melt texturing process. For BiSSCO based compounds, sol–gel and polymer matrix methods have been studied and developed with the achievement of promising critical current densities at 77 K

Routes to obtain high performance, high Tc superconducting bulk materials

International audienceThis paper reviews our investigations for understanding the fundamental relations between physical properties, crystal chemistry, phases relation and processings on the compounds YBa2Cu3O7−x and Bi(Pb)2Sr2Ca2Cu3O10+x. These two systems have in common the complexity of their crystal structure and multi-components chemistry which require challenging material processing for applications. In the YBaCuO system, horizontal bridgman and melting zone processes have demonstrated the possibility of obtaining high performances in this system, with different shaping. A high reproducibility with low material losses have been achieved with a top seeding melt texturing process. For BiSSCO based compounds, sol–gel and polymer matrix methods have been studied and developed with the achievement of promising critical current densities at 77 K

EBSD study on YBCO textured bulk samples: correlation between crystal growth and 'microtexture'

This work describes an electron backscattered diffraction (EBSD) study of the perovskite-derived structures YBa2Cu3O7-delta. After having pointed out the difficulties of EBSD analyses in resolving the orientations of these pseudo-cubic structures, various YBaCuO bulk samples are analysed and the correlation between the microstructure, crystal growth and global texture, determined by neutron diffraction, is carried out. Homogeneous 'microtexture' with small subdomain misorientation of 12 degrees are measured for YBCO top seeding melt textured growth (TSMTG) samples. YBCO perforated samples also exhibit misoriented subdomains, giving rise to a heterogeneous 'microtexture' correlated to the YBCO growth front and to the pattern used for the perforating