Onset Critical Temperature Research Articles

Reactivity of Ba-Y-Cu-O Superconductin Oxide with Substrate Materials

The reactivity of Ba2YCu3O7 to metal oxides and carbonates was studied to develop a substrate material for superconducting oxide films, The superconducting oxide of Ba2YCu3O7 reacted with most of the conventional substrate materials to form oxide compounds. BaZrO3, SrCO3, and CaSiO3 were less reactive to Ba2YCu3O7, and the onset critical temperature of Ba2YCu3O7 remained unaltered after heating with these materials at 1223K. Zero resistivity temperature (Tc (end)), however, decreased depending on these materials. Coexistence of the substrate materials during heating increased the amount of oxygen vacancies in Ba2YCu3O7, resulting in an increased lattice constant of c axis of Ba2YCu3O7, The substrate materials for preparing high Tc superconducting oxide films require no interaction with the amount of oxygen vacancy of Ba2YCu3O7 in addition to the low chemical reactivity to Ba2YCu3O7, CaSiO3 and BaZrO3 were excellent substrate materials.

Laser-induced forward transfer: A new approach for the deposition of high Tc superconducting thin films

We propose in this work a new approach, named laser-induced forward transfer, for the rapid deposition and patterning in a clean environment of high Tc superconducting thin films. A stoichiometric high Tc compound is initially deposited in a thin layer on an optically transparent support by laser evaporation or another more conventional technique. By irradiating under vacuum or in air the precoated layer with a strongly absorbed single laser pulse through the transparent support, we are able to remove the film from its support to be transferred onto a selected target substrate, held in contact to the original film. Using this technique, we have successfully transferred with one single pulse, provided by an excimer or a Nd:YAG laser, YBaCuO and BiSrCaCuO precoated thin films on various substrates. The Rutherford backscattering spectrometry experiments do not show any strong modification in the composition of the transferred layer against the source material, and the superconducting phases for the two types of compounds were obtained after subsequent thermal annealing carried out in a furnace around 850–900 °C in O2. For the BiSrCaCuO films transferred onto MgO substrates, we have measured an onset critical temperature of about 90 K with a zero resistance at 80 K.

Laser-induced forward transfer of high-T c YBaCuO and BiSrCaCuO superconducting thin films

For the first time, the deposition of YBaCuO and BiSrCaCuO thin films has been performed by the single-laser pulse-induced forward transfer technique. In addition, the BiSrCaCuO films were successfully converted into the superconducting phase, with an onset critical temperature of about 90 K and a zero resistance at 80 K, by a subsequent thermal anneal in oxygen atmosphere in the 850–900 °C temperature range.

YBCO superconducting thin films prepared by vacuum coevaporation without post treatment in oxygen

Results on low-temperature preparation of superconducting thin films of YBa/sub 2/Cu/sub 3/O/sub x/ are presented. YBCO thin films of 0.5-1.0- mu m thickness were prepared by vacuum codeposition of Y, BaO, and Cu onto both polycrystalline and single-crystal Al/sub 2/O/sub 3/, MgO, and SrTiO/sub 3/ and on Si+SrTiO/sub 3/ and Si+SiO/sub 2/ substrates. The temperature of the substrates was 550-580 degrees C and the partial oxygen pressure in the vacuum chamber was 10/sup -2/ Pa. The preparation of in situ superconducting thin films was successful with all substrates. Maximum critical temperature at zero resistance was T/sub ce/=85 K, the onset critical temperature T/sub con/ being from 90 to 95 K. The authors believe that T/sub con/ represents the maximal critical temperature of grains. Thus, the synthesis of superconducting granules with high T/sub c/ is possible even at a relatively low temperature during the deposition. On the other hand, the zero-resistance critical temperature T/sub ce/ characterizes the intercrystalline boundaries with electrical properties sensitive to diffusion processes from substrate or surrounding atmosphere. Additional oxidation of films (thermal or plasmatic) does not much affect T/sub ce/ near 85 K.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

BiSrCaCuO superconducting thin films prepared by pulsed laser evaporation deposition

The possibility of preparing BiSrCaCuO thin films by laser evaporation in a clean environment has been successfully studied using YAG and excimer ArF lasers. The as-deposited thin films were converted into the superconductive phase by subsequent annealing in oxygen in the 840° C – 870° C temperature range. Zero resistance was achieved at 83 K and the onset critical temperature was 92 K for BiSrCaCuO films with thickness lying from 150 to 500 nm.

New High Temperature Superconducting Oxides. (La1−xSrx)2CuO4−δ and (La1−xCax)2CuO4−δ

Abstract Solid solution systems of (La1−xSrx)2CuO4−δ and (La1−xCax)2CuO4−δ with x=0.05, 0.075, and 0.10 were found to exhibit the superconductivity through a.c. magnetic susceptibility and electrical resistivity measurements. The onset critical temperature for (La0.90Sr0.10)2CuO4−δ was 37 K, the highest among all the superconducting materials ever known, while that for (La0.95Ca0.05)2CuO4−δ was 18 K.

Effect of interstitial hydrogen on Young's modulus and the martensitic transformation of Nb&amp;lt;inf&amp;gt;3&amp;lt;/inf&amp;gt;Sn

The effects of interstitial hydrogen on the elastic softening, the martensitic transformation and the critical temperature of Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn were studied. Using internal friction as a diagnostic tool, it was found that the martensitic transformation temperature is decreased with hydrogen and completely suppressed for ∼ 0.6 at %H. For these small hydrogen additions, the onset critical temperature is increased to ∼ 18.4K. For higher concentrations of hydrogen, Tc decreases as previously reported and softening of Young's modulus is almost entirely suppressed.