Partial substitution Effect of Pb and Mg on the Structural and Electrical Properties of High Temperature (Hg1-xPbxBa2Ca3-yMgyCu4O10+δ) Superconductor

Abstract

superconductor samples with chemical composition (Hg_1-xPb_xBa₂Ca_3-yMg_yCu O_10+δ) were prepared by solid state reaction method. The effect of partial substitution of Pb and Mg on the structural and electrical properties of this compound were studied. The lattice parameters were characterized by using  X-ray diffraction technique and the results showed that all the samples crystallize in tetragonal crystal structure. This technique proved increase in value of lattice constant (c) with increasing in Pb concentration until 0.4 when y= 0 and decreased after this concentration. On the other hand the partial substitution of Mg in Ca showed decreasing in the value of (c) with increasing Mg concentration to (0.2,0.4,0.8,1,1.4,1.6) when the Pb is constant at (0.4), but the value of (c) increased with increasing Mg to (0.6,1.2). Standard four-probe method used in electrical resistivity measurements and the measurements showed an improvement in Tc from (0.1-0.4) and after this concentration Tc value decreased at substitution of Pb in Hg when Mg=0, where the critical temperature increases from 121K to 134K with an increase of  x from 0 to 0.4 and decreases after this concentration to 120K , but for substitution of Mg in Ca the Tc is increased to 135K,136K,139K,142K and 145K with increasing of Mg to (0.2,0.4,0.8,1,1.4) and decreased to 134K,140K and 140K with  increasing concentration of Mg to (0.6,1.2,1.6) while Pb is constant at (0.4). The surface has been investigated by using scanning electron microscope (SEM) and atomic force microscopy (AFM). These tests were shown that all specimens which tested have good crystalline and homogeneous surface .