High-T_c (95 K) As-Grown Superconducting Bi-Sr-Ca-Cu-O Thin Films

Abstract

From an analysis of the dispersion of indicator in steady laminar fluid flow, expressions are derived for the determination of flow in a straight tube in circumstances in which the familiar Stewart-Hamilton relations for indicator dilution do not generally apply, namely when the method of detection of the tagged blood flow depends on the density of the indicator in the system, as with x-ray videodensitometry. The analysis assumes no diffusion of indicator, and is carried out for arbitrary profiles of fluid flow velocity and tube cross-section. Injections of finite width and finite duration are considered, whereby the indicator is distributed over the tube cross-section either uniformly or in proportion to velocity. Spatial resolution of the detector is considered. A new method is proposed to utilise a priori information when the type of flow is known beforehand. The application of the results is illustrated by several examples for cases with laminar flow. The study is theoretical and is intended only as a first step towards the measurement of blood flow in the human circulation.

Excimer laser patterning of superconducting BiSrCaCuO thin films

“…The importance of as-grown processing for superconducting thin films without a high-temperature post-annealing was realized soon after the discovery of the BSCCO system. Particularly, attempts were made to fabricate BSCCO films with a 2223 phase by various deposition methods [1][2][3][4][5][6][7].…”

Ultrathin film preparation of superconducting 2223 Bi(Pb)SrCaCuO by sputter deposition and rapid annealing

“…This processing may make possible the fabrication of high-T c superconducting oxide thin films with smoother surface and better morphology. Recent reports show that films with the 2212 phase [15][16][17] and 2223 phase [18][19][20][21][22][23] prepared by in situ deposition, had zero resistivity at 50-82 K and 70-95 K, respectively. The zero-resistivity temperature of the as-grown films with a 2212 phase reached the same value as the 80 K bulk samples.…”

“…To obtain superconducting thin films with zero resistivity above 100 K and smoother surfaces, we tried to synthesize thin films under various sputtering parameters [19]. These as-grown superconducting films possess a smoother surface and better morphology, however, it was very difficult to deposit as-grown thin films having zero resistivity above 90 K. The preparation procedure of partially substituting Pb for Bi is shown to be effective for obtaining 110 K bulk superconductors [22,23]. Unfortunately, the Pb concentration in as-grown thin films deposited above 660 • C fell to almost zero [22].…”

Παρασκευη Και Μελετη Λεπτων Υμενιων Των Τριων Μελων Της Υπεραγωγιμης Σειρας Bi_2sr_2ca_n-1cu_no_2n+4n=123

“…Η φάση Bi-2223 είναι πολύ δύσκολο να παρασκευαστεί με τη μέθοδο «in-situ» και ιδίως με υψηλό T c , όπως έχει διαπιστωθεί στην πράξη[84,85]. Από τις πρώτες επιτυχείς προσπάθειες ήταν η παρασκευή μονοφασικού Bi-2223[86] (το έτος 1990) με θερμοκρασία μετάβασης Τ<;=95Κ, η οποία πραγματοποιήθηκε σε σύστημα «magnetron sputtering» με τη δημιουργία ενός ενδιάμεσου Sr 2 Ca n .iCu n 0 2 n+4 η= 1,2,3 ενώ επιπλέον, είναι σκόπιμη η εφαρμογή υψηλής θερμοκρασίας υποστρώματος, ώστε να μη σχηματίζονται μίγματα φάσεων. Έτσι η παρασκευή μονοφασικών υμενίων Βί-2212 με κρίσιμη θερμοκρασία T g =88K επιτεύχθηκε με την εναπόθεση «in-situ» από τους J. Auge et al[87] μετά από εκτεταμένη διερεύνηση, στις συνθήκες T"=860°C και P=3.5mbar(= : 2.7Torr) 0 2 , όπου μάλιστα χρησιμοποιήθηκαν υποστρώματα SrTi0 3(100).…”