Ca substituted tetragonal 123 superconductor with Tc above 85 K synthesized in 1–15 atm oxygen overpressure
| Autor: | Pravin K. Narwankar, A. P. B. Sinha, Donald E. Morris |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Materials science
Doping Valency Energy Engineering and Power Technology chemistry.chemical_element Condensed Matter Physics Copper Oxygen Electronic Optical and Magnetic Materials Tetragonal crystal system Crystallography chemistry Phase (matter) Orthorhombic crystal system Electrical and Electronic Engineering Solubility |
| Zdroj: | Physica C: Superconductivity. 169:7-14 |
| ISSN: | 0921-4534 |
| DOI: | 10.1016/0921-4534(90)90282-j |
| Popis: | We report studies on Ca substitution in the Y-Ba-Cu-O system at elevated oxygen pressure. We find that elevated P (O 2 ) increases the solubility range of Ca, and that Ca stabilizes the 123 phase over 247 or 124 in which the oxygen content is less variable. In the 123 phase [Ca x Y( 1− x )Ba 2 Cu 3 O y ], the orthorhombic distortion decreases systematically as Ca increases , and a , b and c /3 become equal at x ≈0.25, as measured by X-ray diffraction. Then the structure remains tetragonal (CaT-123) throughout the extended range of Ca solubility beyond x ≈0.25. The synthesis of CaT-123 has been achieved in oxygen overpressure as small as 1 bar. Doping by Ca is compensated by a corresponding reduction in oxygen content, and T c remains consistently high in CaT-123 (80–86 K), comparable to orthorhombic 123, and in striking contrast to the well-known oxygen deficient tetragonal 123. This work establishes that the controlling factor in determining T c in this class of superconductors is the optimum oxidation (or formal average copper valency), and not any specific oxygen content, ordering into chains, or orthorhombic distortion. |
| Databáze: | OpenAIRE |
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