X-ray absorption near-edge structure study of Bi2−xPbxSr2(Sm0.85Ce0.15)2Cu2O10+y

✍ Scribed by G. Liang; Q. Yao; S. Zhou; D. Katz

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 215 KB
• Volume: 424
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2005.05.011

✦ Synopsis

Near-edge X-ray absorption spectroscopy results of Ce L 3 -, Pb L 3 -, Bi L 3 -, and Cu K-edge for Bi 2Àx Pb x Sr 2 (Sm 0.85 -Ce 0.15 ) 2 Cu 2 O 10+y (0 6 x 6 1) series are presented. Ce in this series is found to be in a valence state similar to that in CeO 2 . The lack of the 2p ! 6s transition feature in both the Bi and Pb L 3 -edge spectra indicates that Bi and Pb have valence values close to +3 and +2, respectively. With the Pb substitution level x increasing from 0.0 to 0.6, the Cu valence v K increases from 2.20 to 2.34, indicating that the substitution of Bi 3+ by Pb 2+ draws electronic charge out of the CuO 2 layers, increasing the oxygen hole concentration as well as the superconducting transition temperature T c . We also found that for 0.0 6 x 6 0.6, the Cu valence determined from mean characteristic energy of the Cu K-edge spectra is very close to the formal Cu valence estimated by charge neutrality consideration. The decrease of Cu valence with increase of x for samples with x > 0.6 could be due to the formation of a second phase in these samples.