Fluorine-implanted bismuth oxide superconductors

Abstract

We report for the first time the influence of fluorine implantation in the Bi-Sr-Ca-Cu-O system. The incorporation of fluorine was found to enhance the zero resistance temperature and to sharpen the high-temperature transition. The fluorinated sample exhibited Tc (R=0)=89 K and the high Tc phase of the composition had Tc (on) as high as 124 K with an extrapolated Tc (end) of 114 K. Resistance temperature characteristics of a sample before and after fluorine implantation are presented.

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

“…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.…”

“…Watanabe et al [6] on the other hand reported on the observation of a T c = 117.5 K in a single sample prepared by solidstate reaction with BiF 3 as starting reagent. Post-reaction fluorination techniques such as annealing in the presence of NH 4 HF 2 [13,21] or NF 3 [14] did not result in T c improvements, in contrast to F ion implantation that may have a positive effect [11]. Apparently, SrF 2 has not been tested as a starting reagent.…”

Sol-gel preparation and fluorine substitution of BiSCCO high-T c superconductors

“…7). It can be seen in Figs 6,7 that the shapes of these two peaks are quite different: the first one is broad while the second is sharp. An additional small peak at 1128 K was also observed for both samples.…”

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.…”

“…1). For the samples with low fluorine concentration (x < 0.3) (2). The line from the impurity phase SrF 2 is marked with a red dot.…”