Local electronic structure, O–T phase transition and oxygen content in Y0.8Ca0.2Ba2Cu3Oy (y = 6.84 − 6.32) high-Tc superconductors
✍ Scribed by Lingwei Li; Shixun Cao; Fen Liu; Wenfeng Li; Changyun Chi; Chao Jing; Jincang Zhang
- Publisher
- Elsevier Science
- Year
- 2005
- Tongue
- English
- Weight
- 126 KB
- Volume
- 418
- Category
- Article
- ISSN
- 0921-4534
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✦ Synopsis
Y 0.8 Ca 0.2 Ba 2 Cu 3 O y samples with large range of oxygen content, have been systematically studied by means of positron annihilation technology, transport property measurements and X-ray diffraction. The positron lifetime parameters have a strong dependence on oxygen content y, and show evident changes during orthorhombic-tetragonal phase transition (y = 6.50 ± 0.05). The local electron density n e and vacancy concentration C v are evaluated as a function of oxygen content. The correlations between local electronic structure, O-T phase transition and superconductivity are discussed. n e mainly has an effect on high-T c superconductivity, no direct evidence shows that it is related to the O-T phase transition; and C v is mainly caused by oxygen vacancy. The small increase of T c with decreasing y around y $ 6.80 is due to the charge carriers over-doping, which is confirmed by the change of n e in this work.