Thermal properties, texture, second-order stress, and magnetic susceptibility of the [Bi.sub.1.8][Pb.sub.0.3][Sr.sub.2][Ca.sub.2][Cu.sub.3.3][O.sub.x]

• Published in: Journal of thermal analysis and calorimetry 2014-10, Vol.118 (1), p.227
• Main Authors: Harabor, Ana, Rotaru, P, Harabor, N.A
• Format: Article
• Language: English
• Subjects: Adsorption; Crystals; Structure; Superconductors; Thermal properties
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-014-4010-1

Mono-phase high critical temperature (Bi,Pb)-2223 superconductor from the off-stoichiometric [Bi.sub.1.8][Pb.sub.0.3][Sr.sub.2][Ca.sub.2][Cu.sub.3.3][O.sub.x] belonging to the tetragonal system, has been obtained. We studied the crystalline structure, the stress of second order, and the texture of the surface pellet, in the framework of XRD diffractometry. Results of the thermal measurements made in the nitrogen, with a heating rate of 10 K [min.sup.-1], from room temperature (RT) to 1273.15 K, show a slow mass decrease of 1.25 % from RT to 1003.15 K probably due to the elimination of water, oxygen, and of the other gases accumulated on the crystallite surface through chemical adsorption. Two endothermic processes were evidenced on DSC, and DTG curves: the first in the range of 1135.15-1193.15 K (melting and slow decomposition), and another after 1217.45 K (decomposition). The contribution of crystal lattice to the estimated specific heat capacity was in conformity with the Einstein model, giving for the Einstein temperature a value of 1297.5 K. In conformity with the Muller critical state model, we found linear dependences for intragrain critical transition temperature, [T.sub.g], and intergrain coupling temperature, [T.sub.p], versus the amplitude of the external AC magnetic fields. There was evidenced that intergrain critical currents are five orders smaller than the intragrain critical currents.