ELSEVIER PhysicaC276 (1997) 270-276 PHYSICA @ Hg-1212 and Hg-1223 single crystals" synthesis and characterisation R. Gatt a,*, E. Olsson a A. Morawski b, T. Lada b A. Paszewin b, I. Bryntse c, A.M. Grishin d, Yu. Eeltsev e, p. Berastegui f, L.-G. Johansson f a Department t~fPhysics. Chalmers Unicersity of Technology, S-41296 Gothenburg, Sweden b High Pressure Research Center Unipress, Polish Academy of Sciences, Warsaw, Poland c Department of Inorganic Chemistry,'Arrhenius Laboratory., Stockholm University, S-10691 Stockholm, Sweden d Department of Condensed Matter Physics, Royal Institute of Technology, S-10044 Stockholm, Sweden e Department of Solid State Physics, Royal Institute of Technology, S-10044 Stockholm, Sweden J Department of lnorganic Chemistry, Chalmers Universi~' t~f Technology, S-41296 Gothenburg, Sweden Received 25 July 1996; revised manuscriptreceived l February 1997 Abstract Single crystals of HgBa2CaCu206+ 8 (Hg-1212) and HgBa2Ca2Cu3Os+ ~ (Hg-1223) were grown from the melt at an argon pressure of 10 kbar. Electron microscopy, as well as single crystal X-ray diffraction studies show that the crystals are well ordered, The EDS analysis indicates the presence of a minor amount of other cations replacing Hg, Ba and Ca in the structure. Refined fractional coordinates and thermal parameters are given for a crystal of Hg-1223 type. Magnetic and resistive measurements show a T~ of 133 K for the Hg-1223 phase. Keywords: Hg cuprates; Single crystals; Synthesis; High pressure; Liquid phase epitaxy; Scanning electron microscopy; Transmission electron microscopy I. Introduction The Hg cuprates [1] exhibit the highest critical temperature (Tc) for a superconducting transition obtained so far (135 K at ambient pressure for HgBa2Ca2Cu 308 ÷ ~ (Hg- 1223)). They also present a remarkable increase of T~ under high pressure. These compounds attracted much interest because of possi- ble applications as well as from the point of view of * Corresponding author. fundamental science. The possibility to produce elec- tronic devices based on high temperature supercon- ductors (HTS) and operating at temperatures higher than 100 K is appealing. This is not only because of the possibility of using unconventional cooling meth- ods like operating in space and solid state coolers, but also because the performance of these devices at 77 K is expected to be greatly improved in compari- son to devices based on conventional HTS com- pounds like YBa2Cu3OT_8, as they will operate well below their critical temperature. In that respect a minimal value of 120 K for T~ has been suggested [2]. Following that line we have grown thin films of 0921-4534/97/$17.00 Copyright © 1997 Elsevier Science B.V. All rights reserved. PII S0921-4534(97)00051-8