Effect of fluorine doping on phase formation and properties of Bi(Pb)-2223 ceramics

Influence of SrF2 on the Formation, Microstructure and Critical Temperature of (Bi,Pb)2Sr2Ca2Cu3O10 Polycrystalline Samples

“…just before the DTA measurements) results in a faster decrease, suggesting a different interaction mechanism. It can be noted that CaF 2 was also reported to induce a lowering of the partial melting taking place in Bi2223 precursor powders [18], like most other additives and/or dopants, for which thermal analysis data have been reported [27][28][29][30][31]. Trace additives thus appear as a potential general route for lowering the processing temperature of Bi2223.…”

“…This interest originates in an early report by Horiuchi et al [1] showing a clear enhancement of the critical temperature (T c ), when a part of the CaCO 3 powder used for the solid-state reaction synthesis is replaced by CaF 2 . However, whereas improvements were confirmed in some further reports [2][3][4][5][6][7][8][9], in many instances, no increase of T c could be observed [10][11][12][13][14][15][16][17][18][19][20]. The discrepancies might be related to the various synthesis techniques tested for doping the Bi2223 phase with fluorine.…”

“…The discrepancies might be related to the various synthesis techniques tested for doping the Bi2223 phase with fluorine. Lee et al [3] obtained a T c of 116 K in samples produced by reacting a mixture of Bi 2 O 3 , PbO, SrCO 3 , CaCO 3 , CaF 2 and CuO at 838 • C. However, in a recent work by Amira et al [18], a similar preparation technique with CaF 2 yielded T c values limited to less than 110 K. Wei et al [2] used CuF 2 instead of CaF 2 as a fluorine source and could observe superconducting transitions at up to 118 K, but more recent reports on the use of CuF 2 in a solid-state reaction route did not succeed in reproducing this promising result [7,19,20]. According to Gao et al [4], using PbF 2 amongst the starting reagents instead of PbO results in a T c as high as 121 K, but here again, no confirmation was achieved by other groups, neither using solid-state reaction routes [9,15,17], nor sol-gel techniques [8,10].…”

NMR and EPR spectroscopic studies of fluorinated Bi-2212 HTSC

“…The research on the influence of fluorination on the properties of Bi-containing HTSC has not given clear results. Some authors [2][3][4] claim that fluorination of the Bi-Sr-Ca-Cu-O system causes an increase of the critical temperature by 5-10 K. Other researchers [5][6][7] say that the critical temperature of the obtained superconducting samples does not change, because the fluorine atoms do not occupy positions in the {CuO 2 } n chains, which are responsible for carrying the superconductive current. The authors of [8] report that the critical temperature of the (Bi-2223)F phase falls down to 71-75 K.…”

Some effects of the doping with alpha - Al_2O_3 nanoparticles in the transport properties of Bi_1.65 Pb_0.35 Sr_2Ca_2 Cu_3O_y ceramic superconductors

“…Moreover, the pinning potential is one of the basic parameters that defines the performance of a superconducting material for commercial and technological applications [3]. In general, the granular superconducting materials can be modified into a material with better transport properties, for example: varying the compacting pressure [4,5], varying the sintering time [6], by chemical doping and nanosized particles addition [7][8][9][10]. For example, Ghattas et al [3] analyzed the effects of α-Al 2 O 3 NPs addition on the microstructure and pinning properties of polycrystalline (Bi,Pb)-2223 samples.…”