Nature of the superconducting transition in high Tc Tl-Ca-Ba-Cu-O compounds: Positron annihilation studies

✍ Scribed by P.K. Pujari; T. Datta; Satya Prakash; S.B. Manohar; I.K. Gopalakrishnan; G.M. Phatak; J.V. Yakhmi; P.V.P.S.S. Sastry; R.M. Iyer

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 608 KB
• Volume: 159
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(89)90106-8

✦ Synopsis

Pb2Sr2_xLa~Cu206+~ has a structure, which can be derived from that of PbzSrzCal _xYxCu3Os+a, by removing a CuO 2 and (Ca, Y) layer. The until cell parameters for the composition with x= 1.0 are a=0.5333(2), b=0.5421 (2), c= 1.2609(6) nm with space group P22t2. The onset of the superconducting transition temperature is 32 K with zero resistance at 26 K for x= 1.2, whereas for other compositions a broader transition is observed. Partial replacement of Pb by Bi leads to a decrease in T~. Heating in air at 500 °C leads to a transformation to tetragonal symmetry, which can be reversed by beating in nitrogen at 500 ° C.