C. Richard Guarnieri

Thin‐film Bi‐Sr‐Ca‐Cu‐O high‐temperature superconductors using pulsed laser evaporation from sintered disks

Films of the high‐temperature superconductor in the Bi‐Sr‐Ca‐Cu‐O system were deposited by pulsed laser evaporation from a ceramic disk. Films deposited onto (100) MgO show x‐ray diffraction patterns characteristic of c‐axis textured Bi2(Sr,Ca,Bi)3Cu2Ox phase following annealing for 10 min at 850 °C in 20% O2‐80% N2. These textured films have zero resistance at 78 K and show resistance drops near 110 K. The effects of the annealing environment on the electrical and structural properties are presented.

Absence of chain oxygen outgassing from ion‐bombarded YBa2Cu3O7−x

We report an investigation of possible oxygen loss from an ion‐bombarded YBa2Cu3O7−x superconductor. The chain oxygen sites in thin‐film samples were filled with 18O, and the 18O content of the films measured as a function of irradiating ion dose using the 18O(p,α)15N nuclear reaction. Absolute measurement of the 18O concentration was achieved by the use of a Si18O2 standard. No significant change in the 18O concentration was detected after irradiation with 2×1014 2 MeV As ions/cm2, which is a dose sufficient to raise the resistivity of the samples by a factor of 104. We conclude that ion irradiation does not cause oxygen to outgas from the chain sites. This implies that ion bombardment effects in YBa2Cu3O7−x are due to radiation‐induced defects.

Plasma spray deposited superconducting YBa2Cu3O7 films

Superconducting YBa2Cu3O7 films have been deposited by the plasma spray deposition process. The sequence of processing steps, including powder preparation plasma deposition, and post‐deposition treatment were studied to optimize Tc and minimize process complexity. The as deposited film can be varied in a controlled way from poorly crystalline to the desired orthorhombic YBa2Cu3O7 phase. Plasma temperature, residence time in the plasma, and substrate temperature were used to control the phase of the as‐deposited film. With high temperature (930°C) followed by low temperature (470°C) anneals, well crystallized YBa2Cu3O7 films were grown on a variety of substrates. Depending on substrate interactions, completion temperatures range from 84 K to <50 K. To minimize substrate interactions, crystallization studies were done to optimize post‐deposition heat treatment schedules.