Ceramics-Silikáty 49 (1) 23-28 (2005)

EFFECTS OF POST-OXYGEN ANNEALING AND LANTHANUM DOPING ON INTER- AND INTRA-GRAIN PROPERTIES OF (Tl,Pb)-1223 SUPERCONDUCTORS

A. Cigáň, G. Plesch, J. Maňka, F. Hanic, M. Kopčok, A. Koňakovský, J. Kliment

Effects of oxygen annealing and low level La³⁺ doping of the (Tl,Pb)-1223 system have been investigated. Samples with the nominal composition (Tl_0.6Pb_0.5)(Sr_0.8Ba_0.2)₂Ca₂Cu₃O_8+d - x LaO_1.5, where x ranges from 0.00 to 0.10, were synthesized using a sol-gel process. Their superconducting inter- and intra-grain properties, phase compositions, and microstructure were stu-died. XRD results prove that (Tl,Pb)-1223 is the dominant phase in all samples. The La doping initiates a formation of the (Tl,Pb)-1212 phase and decreases the volume superconducting properties. The post oxygen annealing strongly improves intergrain superconducting links and leads to a positive effect on the critical temperature, Tcon and the DTcon. The central peak of magnetization hysteresis loops around zero field is found to be in an anomalous positive position on the descending branch of the external field.

Keywords: (Tl,Pb)-1223 based superconductors, La³⁺ doping, Magnetization, SQUID gradiometer, Ageing