ELSEVIER Physica C 268 (1996) 143-149 PHYSICA The effect of Ag diffusion on properties of BiPbSrCaCuO thin films T.D. Dzhafarov l, A. Varilci, M. Sadygov l, M. Altunba~ * Department of Physics, Faculty of Science and Arts, Karadeniz Technical University, 61080 Trabzon, Turkey Received 29 April 1996 Abstract Superconducting BiPbSrCaCuO films have been evaporated on Ag/MgO and MgO substrates (with and without Ag buffer layer) by the electron-beam technique. The influence of annealing temperature on the crystalline structure and superconducting properties of BiPbSrCaCuO films was investigated by X-ray diffraction, X-ray fluorescence spectroscopy, scanning electron microscopy, critical temperature, critical current density and room temperature resistivity measurements. It was shown that the annealing of both types of films at 835°C or 845°C resulted in formation of the mixed Bi-2223 and Bi-2212 phases with a high degree of preferential orientation with the c-axis perpendicular to the substrates. Annealing of films on Ag/MgO substrates is additionally accompanied by Ag diffusion from the buffer layer into BiPbSrCaCuO films. The higher rate of crystallization of the Bi-2223 and Bi-2212 phases, the higher degree of c-axis orientation, the higher dense surface morphology, the reduced lattice parameter c (by 0.6-0.8%) the reduced room temperature resistivity (2-3 times), the significantly enhanced critical temperature (T c ffi 106 K at R = 0) and the critical current density (Jc = 1.1 × 104 A/cm 2 at 77 K) were observed for the Ag-doped films (on Ag/MgO substrates), in comparison with those for the undoped films (on MgO substrates). The temperature dependence of the Ag diffusion coefficient in Bi-2212 films in the range 650-800°C was described by the relation D ffi 2.2 × 10 -5 exp(- 1.2/kT). 1. Introduction Technical advantages of silver addition in the bulk BiPbSrCaCuO superconductors which include decreasing of melting temperature and accelerating the formation of Bi-2223 and Bi-2212 phases [1-6], development of the strong texture with c-axis [2,7,8], decreasing of the lattice parameter c [8,9], improve- ment of mechanical ductility [10], decreasing of the room temperature resistivity [8,11,12], increasing of * Corresponding author. Fax: +90 462 325 3195. i Permanent address: Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan. the critical current density [13,14] and the critical temperature [5,8,15] have been extensively studied. The epitaxial and strongly textured thin films of the high-temperature BiPbSrCaCuO superconductors which show very high transport properties present particular interest for the superconductive electron- ics. The possibility of realizing high-quality thin films of cuprate materials is an important step in the investigation of their superconducting properties, as well as a large variety of applications, However reports on the influence of Ag doping on the crys- talline structure and properties of BiPbSrCaCuO thin films are relatively rare. Chae et al. [16] showed that Ag-doped BiSrCaCuO thin films grown on Ag sub- 0921-4534/96/$15.00 Copyright © 1996 Published by Elsevier Science B.V. All rights reserved.PH S0921-4534(96)00411 -X