SUPERCONDUCTIVITY ABOVE 250K IN TL1.8BA2.0CA2.6CU3.0O10-PRESSURE(DELTA AT HIGH)

The pressure dependence of the superconducting transition temperature T-c (onset) of Tl1.8Ba2.0Ca2.6Cu3.0O10+delta (T1-2223) has been measur ed under quasi-hydrostatic pressure (QHP) up to 5.0 GPa. The T-c incre ases with increasing pressure at a relatively high rate and reaches a maximum at 255.4 K and pressure of about 4.3 GPa. This is the highest T-c yet observed for any high-T-c superconductor. The total change in T-c from ambient condition (T-c = 129 K) to the high pressure applied can be greater than 126 K. The T-c above 200 K was replicated several times in our experiments. The site of the maximum of T-c and the value of dT(c)/dP = 1.7 K/GPa (at P=0) agree with previous results obtained by D. Tristan Jover et al. (Physica C 218, 24 (1993)) and J. G. Lin e t al. (Physica C 175, 627 (1991)), respectively. (C) 1998 American Ins titute of Physics.