Effect of Cr and V substitution on the properties of bulk Tl-based superconductors

Abstract Bulk TlBaCaCuO superconducting samples have been used to analyse the effect of Cr and V doping on the intergranular properties. The a.c. magnetic susceptibility has been measured as a function of temperature and a.c. magnetic field amplitude up to 14 000 A m −1 as well as the resistivity as a function of temperature and d.c. applied magnetic field up to 795 kA m −1 . For the samples doped with Cr an enhancement in the intergranular critical current density was observed; the sample doped with V gave results similar to those obtained for the undoped Tl compound. The role of Cr and V in these materials is discussed in terms of the electrical and magnetic measurements performed. Additionally, measurements of the resistance versus temperature and applied d.c. field may help to elucidate the behaviour of the irreversibility line in these Tl compounds.