Bismuth Valence Studies of As-Grown Superconducting Bi-Sr-Ca-Cu-O Thin Films with T_c(zero) from 98 K to 66 K

Abstract

Bismuth valence of Bi-Sr-Ca-Cu-O superconducting film has been studied by X-ray photoemission spectroscopy. As-grown highly oriented Bi-Sr-Ca-Cu-O 2223 single-phase films with various critical temperatures from 98 K to 66 K were prepared by changing the Bi content. The Bi 4f core level electron spectra are decomposed into two components. These components are assigned to BiO and to Bi2O3 which is located at an energy higher than the peak of BiO by about 1 eV. Then it was empirically determined that the critical temperature can be controlled by the Bi mean valence, and changes irrespective of the number of Cu-O planes. The critical temperature of the film increases with a decrease in the Bi mean valence which was calculated from the ratio of BiO/Bi2O3.

Catalytic Ozonation over Ca2Fe2O5 for the Degradation of Quinoline in an Aqueous Solution

“…The Ca element at a binding energy of 345.6 eV can be attributed to a nonstoichiometric oxide as Ohbayashi has reported. 30 The XPS spectrum of the Fe 2p 3/2 region in fresh and used Ca 2 Fe 2 O 5 catalyst can be split into two peaks (Figure 6b). The peak at 709.5 eV was attributed to Fe 2+ .…”

High‐resolution XPS studies of superconducting Ag/(Bi0.9Pb0.1)2.3Sr2.0Ca1.9Cu3.0O10+x tapes and wires

“…The intensity of this feature correlates with the critical temperature (and hence the ratio of 2223/2212 present in the samples). 35 These authors attribute it to reduced 'BiO-like' Bi. 35 In our own data, however, the feature appears at -2 eV below the main peaks, a discrepancy that is probably not wholely explained by the difference in resolution between the two measurements.…”

“…35 These authors attribute it to reduced 'BiO-like' Bi. 35 In our own data, however, the feature appears at -2 eV below the main peaks, a discrepancy that is probably not wholely explained by the difference in resolution between the two measurements. In addition, the feature is largest in our data where the proportion of 2223 is lowest, which is exactly the reverse of that seen by Ohbayashi et aL3' The extremely low binding energy of the features is consistent with the presence of metallic Bi (0),j6 and indeed this assignment has been made by other authors studying mixed-phase 2223/2212 samples.25 However, given the repeated oxidizing calcining cycles that the samples have been subjected to, it must be extremely unlikely that Bi is present in this oxidation state.…”

Comment on ‘‘Universal relationship betweenTcand the hole content inp-type cuprate superconductors’’

“…Recently, there has been a weight of evidence that the valence states of Bi and Tl are less than 3+ [10][11][12][13] and can undergo variation, which has also been theoretically substantiated [14][15][16]. As a consequence of the simultaneous presence of two mixed valence cations, viz., Tl and Cu (or Bi and Cu), the task of estimating the copper valence, and hence the hole concentration, in both Tl-and Bi-based cuprates is seemingly an unsolved problem through the iodometric technique and, thus, the results yielded by the latter are not free from ambiguity.…”

“…As a consequence of the simultaneous presence of two mixed valence cations, viz., Tl and Cu (or Bi and Cu), the task of estimating the copper valence, and hence the hole concentration, in both Tl-and Bi-based cuprates is seemingly an unsolved problem through the iodometric technique and, thus, the results yielded by the latter are not free from ambiguity. Moreover the T c of these systems is not only dependent on the number of holes in Cu, but is also controlled by the valence state of Bi and Tl [10][11][12][13].…”