Analysis of fluorine incorporation into YBa2Cu3O6.5+δ by means of X-ray emission spectroscopy

X-ray emission and photoelectron spectra, and the location of fluorine atoms in strontium and calcium copper oxyfluorides

“…These spectra correspond to the dipole transition 2p → 1s (vacancies on the F 1s core level are filled by valence F 2p electrons) and give information about the F 2p density of states in the valence band. It is shown in our previous publications [13,14] that these spectra are very sensitive to the chemical bonding and show a different energetic position and intensity of the high-energy satellite (at E ∼ 680-682 eV) according to the chemical bonding. It is seen from the spectra given in figure 6 that F Kα XES of Sr 2 CuO 2 F 2+δ and Ca 2 CuO 2 F 2+δ are different and, on the other hand, are very similar to the spectra of SrF 2 and CaF 2 , respectively.…”

Microstructure and superconducting properties of top-seeded melt grown YBa2Cu3O7 bulks doped with BaF2

“…Perrin et al [11] and Fedorenko et al [10] consider that no clear evidence for fluorine insertion in the Y123 structure was given by authors who added BaF 2 in the powder mixtures. Moreover, Wang et al [4] who have added BaF 2 to their mixtures affirm from 19 F NMR measurements that 95 ± 5% of the BaF 2 remained unreacted.…”

“…This effect is consistent with the presence of fluorine atoms in the Y123 matrix that could reduce the oxygen diffusion rate. Indeed, by means of x-ray emission spectroscopy, Fedorenko et al [10] have found for fluorine-doped samples through NH 4 HF 2 annealing that fluorine atoms are substituted with oxygen atoms in the CuO 2 planes.…”

“…F 2 gas was first tested but was reported as too aggressive [8]. Annealing under a NH 4 HF 2 atmosphere near 300 • C was performed by Rao et al [9] or Fedorenko et al [10]. Fedorenko et al [10] only studied the incorporation of fluorine in the Y123 matrix but Rao et al [9] did not report significant change in the T c .…”

“…Annealing under a NH 4 HF 2 atmosphere near 300 • C was performed by Rao et al [9] or Fedorenko et al [10]. Fedorenko et al [10] only studied the incorporation of fluorine in the Y123 matrix but Rao et al [9] did not report significant change in the T c . Perrin et al [11] have shown that under a NF 3 gas atmosphere, below 250 • C no reaction occurs whereas above 340 • C, the Y123 compound is decomposed.…”