ELSEVIER Physica C 260 (1996) 93-102 PHYSICA AC losses and critical currents in Ag/( T1,Pb,Bi)-1223 tape M. Ciszek a, * ,1, B.A. Glowacki a,2, S.P. Ashworth a, A.M. Campbell a, W.Y. Liang a, R. Flilkiger b, R.E. Gladyshevskii b a IRC in Superconductivity, University of Cambridge, Cambridge CB30HE, UK b DEpartement de Physique de la Mati~re Condens~e, Universit~ de Gen~ve, 24 quai Ernest Ansermet, CH-1211 Gen~ve 4, Switzerland Received 9 December 1995; revised manuscript received 18 January 1996 Abstract The results of AC loss measurements of silver-sheathed (TI,Pb,Bi)-1223 tapes prepared by the powder-in-tube method are presented. Losses arising from an external AC magnetic field are compared with those generated by AC transport currents (self-field losses). Experimental results, obtained by both methods, show that energy losses are purely hysteretic in nature in the range of applied frequencies (30-200 Hz). Critical current densities are derived from the magnetic-loss data and compared with those measured by the four-point transport method. Further, the dependence of the transport critical currents on the external DC magnetic field, for different geometrical configurations of the tapes with respect to the field, i.e. field parallel or perpendicular to the plane of the sample, are presented. The experimental results are compared with theoretical predictions based on the critical-state model. 1. Introduction The practical large-scale applications of high-T~ superconductors (HTS's) are limited by the magni- tude of the electric current which can be transported through the material without dissipation. Factors which limit the current-carrying capability of HTS's are mainly their granular nature and the strong anisotropy of the electromagnetic properties. How- ever, recent world-wide research and technological progress in developing HTS silver-sheathed tapes, * Corresponding author. Fax: +44 1223 33 70 74; e-mail: mc 10023@hermes.cam.ac.uk. i On leave from Institute for Low Temperature and Structure Research, Polish Academy of Science, Poland. 2 Also at Department of Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB2 3QZ, UK. based on Bi-2223, Bi-2212 and T1-1223 compounds, monofilamentary as well multifilamentary, promises great hope for their technical applications. Silver- sheathed tapes containing T1-1223 superconductor exhibit also high critical current densities Jc versus magnetic field at 77 K as compared to, for example Bi-2223 or T1-2223 materials [1]. This is ascribed to the presence of only a single insulating (T1-O) layer between the Cu-O planes in the T1-1223 ceramic, leading to enhanced Josephson coupling along the c-axis, (which in turns leads to stronger flux pinning) and hence to a three-dimensional charge-transfer character, rather than the two-dimensional character of the bismuth 2212 and 2223 materials. Moreover, T1-1223 compounds exhibit a higher irreversibility line, in comparison with, for example, bismuth ce- ramics [1-3]. The high Jc and the three-dimensional- ity of the T1-1223 make it a potentially valuable 0921-4534/96/$15.00 © 1996 Elsevier Science B.V. All fights reserved PH S0921-4534(96)00097-4