Journal of ALLOYS AHD COMPOUNDS ELSEVIER Journal of Alloys and Compounds 239 (1996) 142-146 Magnetic field dependence of samples of nominal composition Bil.6Pb0.4Sr2Ca3Cu4Oy (2234) prepared by various techniques E. Yanmaz, I.H. Mutlu 1, S. Nezir, M. Altunbas Karadeniz Technical University. Faculty ()[ Arts and Sciences, Department o[" Physics, 61080 Trabzon, Turkey Received 13 October 1995; in final form 4 January 1996 Abstract The effect of magnetic field was investigated by measuring the resistivity as a function of temperature in different magnetic fields on Bil 6Pb, 4Sr~Ca3Cu40 `` (2234) samples prepared by solid state reaction, ammonium nitrate and melt quench methods. It was found that the transition temperatures T of samples changed with changing magnetic fields. The amount of change was found to be dependent on the sample preparation technique. The samples prepared by solid state reaction and ammonium nitrate methods were affected by magnetic field more than melt quench-annealed samples. Additionally, the critical current density J~ of samples decreased with increased magnetic field. Keywords: BSCCO system; Magnetic field dependence; Preparation methods: Transition temperature 1. Introduction After the discovery of La-Ba-Cu oxide superconduc- tors [1], many works have been reported, finding new superconducting oxides and researching their physical properties. The physical properties common to all high-T c superconductors were summarized by Tanaka [2], for example low carrier concentration, control- lability of carrier concentrations, existence of semi- conductor phase, appearance of antiferromagnetism in semiconductor phase and two-dimensionality, etc. All high-T~ superconducting materials have two- dimensional (2D) CuO 2 planes in their crystal struc- ture. The electrical conduction is mostly in the CuO planes, and it is expected that the high-T~ supercon- ductivity will appear in the CuO plane. It is well known that the high-T~ superconductors are very sensitive to material defects [3]. For instance, a small amount of oxygen deficiency and some disorder in the crystal structure affect the critical temperature of the superconductor. The purpose of this work is to investigate sys- Permanent address: University of Harran, Faculty of Arts and Sciences, Dept. of Physics, Sanliurfa Turkey. 0925-8388/96/$15.00 © 1996 Elsevier Science S.A. All rights reserved PII S0925-8388(96)02231-1 tematically the magnetic field dependence of BiL.6Pb0.4SrzCasCu40 v (2234) samples produced using different preparation methods [4]. Our analysis makes it possible to obtain fairly reliable information on some physical properties of these materials. It was found that the transition temperature T~ and the critical current density Jc of samples changed with increasing magnetic field. 2. Experimental procedure Commercial powders of 3N purity, Bi20 3, PbO, SrCO 3, CaO and CuO in the stoichiometric ratios of Bi~6Pb04S2Ca3Cu40 ~, (2234), were well mixed by milling. To achieve superconductivity, this starting composition was treated in three different methods, as follows. 2.1. Solid state reaction method The above composition was calcined at 840°C for 10 h and slowly cooled to room temperature. The calcined powders were pressed into pellets and then annealed at 845°C for 100 h in air.