Stabilizing the Tl-1223 phase by doping with tellurium

Abstract

Te-doping of (Tl 0.54 Pb 0.5−x Te x )(Sr 0.85 Ba 0.15 ) 2 Ca 2 Cu 3 O y superconductors with x ranging from 0 to 0.1 has been investigated. Small amounts of Te (x < 0.05) strongly favoured the formation of the Tl-1223 phase in bulk samples, leading to phase-pure material. The concentration of the Tl-1212 phase was below the detection limit of the x-ray diffraction. The critical temperatures of bulk phase Tl-1223 for x = 0.02 were 120 K. The transition widths narrowed and the critical current densities for bulk phase material increased upon addition of small amounts of Te. At higher doping levels, Ba 2 CuTeO 6 appeared as a secondary phase but the remaining material was still high-purity Tl-1223 phase. (Tl 0.54 Pb 0.48 Te 0.02 )(Sr 0.85 Ba 0.15 ) 2 Ca 2 Cu 3 O y films on lanthanum aluminate substrates prepared by screen printing of the precursor and followed by ex situ thallination, lead to highly c-axis oriented and ab-aligned samples with critical temperatures T c(0) of 117 K and transition widths T (90-10%) of 1 K. Critical current densities of 1.15 × 10 10 A m −2 were achieved for 1.5 µm thick films in self-field at 77 K. The critical current densities at 0.8 T and 77 K were 7.4 × 10 9 A m −2 for H ab and 0.7 × 10 −9 A m −2 for H c.

Preparation and characterization of (Tl, Pb)(Ba, Sr)-1223 films on untextured silver

“…The Tlbased materials are considerably less sensitive to moisture than other high-temperature superconductors, such as the yttrium-barium cuprates. Preparation and phase formation can be easily performed by in situ thallination of the precursor material [2,3]. Oxygen stoichiometry can be achieved without too many difficulties.…”

Critical Currents of Tl2Ba2Ca2Cu3Oz Bulk Superconductors

“…The critical temperatures of bulk Tl-2201 [5], Tl-2212 [6] and Tl-2234 [7] are 90, 118, and 116 K, respectively. For Tl 1 Ba 2 Ca n−1 Cu n O z (Tl-12(n-1)n) homologous series the maximum critical temperature is of the order of 120 K and occurs also for three oxygencopper layers [8]. The critical temperatures for these system depend also on some other factors.…”

Electrochemical processing of Tl-2223 films with conducting heterostructure substrates

“…Recent studies have shown that the Tl-1223 phase has the best superconducting properties in magnetic fields [3]. Preparation and phase formation can be easily performed by in situ thallination of the precursor material [4,5]. Oxygen stoichiometry can be achieved without too many difficulties.…”