Polymerized complex synthesis and intergranular coupling of Bi-Pb-Sr-Ca-Cu-O superconductors characterized by complex magnetic susceptibility

Abstract

Superconducting Bi-Pb-Sr-Ca-Cu-O ceramics have been synthesized by the polymerized complex method at the Bi1.8Pb0.2Sr2Ca2Cu3Oy, Bi1.6Pb0.4Sr2Ca2Cu3Oy and Bi1.68Pb0.32Sr1.75Ca1.82Cu2.83Oy compositions. The polymerized complex method includes three important major steps: (1) formation of stable citrate complexes uniformly dispersed into ethyleneglycol and water, (2) fabrication of polymerized complexes which are formed through dehydration (or esterification) between ethyleneglycol and metal-citrate complexes, and (3) pyrolysis of the polymerized complex precursor and the subsequent heat treatments for producing the Bi-Pb-Sr-Ca-Cu-O superconductor. The present technique offers more convenient and easier fabrication of (Bi,Pb)2Sr2Ca2Cu3Oy superconductors compared with other more elaborate preparation procedures based on wet-chemical techniques, as it eliminates many steps such as ageing, filtration, washing, and pH control. ‘‘X-ray-clean’’ (Bi,Pb)-2223 superconductors have been obtained for all the three compositions after sintering at 850 °C in air for 94–235 h, depending upon the nominal composition of the starting batch. Noticeable is that a small deficiency of Sr, Ca, and Cu relative to the ideal stoichiometric composition of the (Bi,Pb)2Sr2Ca2Cu3Oy significantly accelerates the formation of the (Bi,Pb)-2223 phase. Complex magnetic susceptibility measurements show that Tc(onset) of the bulk (Bi,Pb)-2223 phase remains almost constant at around 108 K, independent of the compositions. However, it is stressed that low-level and/or amorphous impurity phases possibly concentrated on grain boundaries can have dramatic effects on the overall magnetic properties even for materials which look like very ‘‘clean’’ by x-ray diffraction. The best superconducting properties were obtained with samples with a nominal composition of Bi1.6Pb0.4Sr2Ca2Cu3Oy after sintering in air at 850 °C for 180–280 h. The onset temperature of superconducting transition obtained by complex susceptibility was 108.0 K and the transition width (10%–90%) of full diamagnetism was 5.2 K for a measuring field of 100 mOe.

Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

“…On the other hand, its major drawback could be the high price of substrates. The polymerized-complex method (PCM) also belongs to the wet-chemical methods, however it is different from typical sol-gel methods, as gel is obtained from the solution, not from the colloid [9].…”

Synthesis of NaxCo2O4thermoelectric oxide with crystallographic anisotropy by chemical solution process

“…In a previous study [8], mechanical grinding and SPS (spark plasma sintering) were tried to synthesize the Na x Co 2 O 4 in order to prepare a fine microstructure, but the crystallographic anisotropy was ruined, resulting in a lower thermoelectric performance. In this study, we have applied the polymerized complex (PC) method, which is a kind of chemical solution process, in the synthesis of the Na [9,10]. This method is based on the stable formation of metalcitrate complexes and the following polymerization between ethylene glycol and citric acid complexed with constituent metals, forming the polymeric product with a three-dimensional network structure.…”

Synthesis of Y-Doped n-Type SrTiO<SUB>3</SUB> Thermoelectric Oxides by Polymerized Complex Process

“…On the other hand, there is the polymerized complex (PC) process as one of the chemical solution processes. 11,12) The PC process can provide a fine powder precursor and mix constituent metal elements at atomic level. Therefore, the PC process is also considered to simplify the substitution of Y for Sr site.…”