Positron annihilation study of the O–T phase transition for Eu1+xBa2−xCu3O7−δ superconductors
| Autor: | Guohui Cao, D.N. Zheng, Long Wei, Baoyi Wang, Joseph H. Ross, Ruifei Duan, Z. X. Zhao, Xiaotao Xiong, Yang Li, Yang Liu |
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| Rok vydání: | 2004 |
| Předmět: |
Superconductivity
Phase transition Materials science Condensed matter physics Energy Engineering and Power Technology Crystal structure Condensed Matter Physics Electronic Optical and Magnetic Materials Crystallography Phase (matter) Proximity effect (superconductivity) Cuprate Electrical and Electronic Engineering Type-II superconductor Stoichiometry |
| Zdroj: | Physica C: Superconductivity. 402:179-187 |
| ISSN: | 0921-4534 |
| DOI: | 10.1016/j.physc.2003.09.081 |
| Popis: | The effects of Eu substituting for Ba on structural and superconducting properties were investigated for a series of superconductors Eu 1+ x Ba 2− x Cu 3 O 7− δ ( x =0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, and 0.2). With Eu content increasing, the random substitution of excessive Eu for Ba ion forms a Eu–Ba non-stoichiometric distribution on Ba site, which deviates from the ideal 123 phase stoichiometry. The analysis of crystallographic structure shows that the solid solubility x of Eu on Ba site is over 0.2. Eu 1+ x Ba 2− x Cu 3 O 7− δ take on an orthorhombic–tetragonal (O–T) phase transition from x =0.06, and end in x =0.18. Corresponding to the O–T phase transition, superconducting critical temperature T c rapidly decreases with Eu content increasing, which is attributed to the decline of carrier density and the proximity effects of non-superconducting clusters. The positron annihilation measurements show anomalous changes for lifetime spectra and Doppler-broadened radiation spectra when the O–T phase transition occurs. By the model of excessive oxygen defects in Cu–O chain regions, we discuss effects of Eu–Ba non-stoichiometric distribution on structural and superconducting properties. |
| Databáze: | OpenAIRE |
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