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

Effects of oxygen annealing and low level La3+ doping of the (Tl,Pb)-1223 system were investigated. Samples with the nominal composition (Tl0.6Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3O8-delta-xLaO1.5, where x ranges from 0.00 to 0.10, were synthesised using a sol-gel process. Their superconducting inter- and intra-grain properties, phase compositions, and microstructures were studied. XRD results prove that (Tl,Pb)-1223 is the dominant phase in all samples. The La doping initiates the formation of the (Tl,Pb)-1212 phase and decreases the volume superconducting properties. The post oxygen annealing strongly improves inter-grain superconducting links and leads to a positive effect on the critical temperature, Tc(on) and the DeltaTc(on). The central peak of magnetisation hysteresis loops around zero field is in an anomalous positive position on the descending branch of the external field. 9 refs.