Boyd W Veal

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The dependence of the critical current density Jc on hydrostatic pressure to 0.6 GPa is determined for a single 25 degrees [001]-tilt grain boundary in a bicrystalline ring of nearly optimally doped melt-textured YBa2Cu3Ox. Jc is found to increase rapidly under pressure at +20%/GPa. A new diagnostic method is introduced (pressure-induced Jc relaxation)(More)
The dependence of the critical current density Jc T on hydrostatic He-gas pressure to 0.6 GPa is determined for nearly optimally doped and strongly underdoped melt-textured YBa2Cu3Ox bicrystalline rings containing single 001 -tilt grain boundaries GBs with mismatch angles from 0° to 31°. For all samples with 0°, Jc is found to increase rapidly under(More)
Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen(More)
Structural components that operate at high temperatures (for example, turbine blades) rely on thermally grown oxide (TGO), commonly alumina, for corrosion protection. Strains that develop in TGOs during operation can reduce the protectiveness of the TGO. However, the occurrence of growth strains in TGOs, and mechanisms that cause them, are poorly(More)
The electric transport of the charged particles in a spin texture was investigated in a strongly underdoped YBa2Cu3O6.25 single crystal in order to identify the characteristic electrical transport mechanism. The in-plane resistivity revealed three different regimes of charge transport: a chiral 2D VRH regime up to 55 K with a characteristic temperature Td ≈(More)
We report magnetoconductivity measurements on YBa2Cu3Ox (x56.25 and 6.36) single crystals. Our main result is that both the in-plane Dsab and out-of-plane Dsc magnetoconductivities exhibit the field dependence characteristic of ‘‘two-dimensional’’ quantum interference in applied magnetic fields Huuc . Namely, Dsc ,ab }ln H/H0.0, with Dsc /sc substantially(More)
Strains in thermally grown oxides have been measured in-situ, as the oxides develop and evolve. Extensive data have been acquired from oxides grown in air at elevated temperatures on different model alloys that form Al2O3. Using synchrotron x-rays at the Advanced Photon Source (Beamline 12BM, Argonne National Laboratory), Debye-Scherrer diffraction patterns(More)
Nearly hydrostatic pressures are found to enhance the critical current density Jc through single grain boundaries in YBa2Cu3Ox rings and to induce superconductivity in Li. Whereas Li becomes superconducting above 20 GPa at temperatures as high as 15 K, no superconductivity was observed above 4 K in Na to 65 GPa nor in K above 4 K to 43.5 GPa or above 1.5 K(More)
We report magnetoresistivity measurements on strongly underdoped YBa2Cu3Ox (x56.25 and 6.36) single crystals in applied magnetic fields Hi c axis. We identify two different contributions to both in-plane Drab /rab and out-of-plane Drc /rc magnetoresistivities. The first contribution has the same sign as the temperature coefficient of the resistivity ] ln ri(More)
In-plane and out-of-plane magnetoresistivity ~MR! measurements were performed on the same antiferromagnetic ~AF!YBa2Cu3O6.25 single crystal using a six-lead configuration, in magnetic fields H applied along the ab plane. We identified three terms contributing to both MRs. The first term is anisotropic with respect to the in-plane field orientation, with a(More)