THERMAL-EXPANSION MEASUREMENTS OF YBA2CU3O7 SINGLE-CRYSTALS

Since the discovery of high-Tcsuperconductivity in YBa2Cu307many investigations have been performed to search for crysta structure anomalies at Tc. The existence of a structural change at the superconducting transition is of interest for theoretical models. In the literature there are contradictory statements on the temperature dependence of lattice and Structure parameters. Our x-ray measurements on single crystals indicate that the onset of superconductivity is not connected with a jump in the thermal expansion coefficient cl, as discussed i n literature, but rather we observe a jump i n da/dT. © 1990, Taylor & Francis Group, LLC. All rights reserved.