Structure of Al Defect in High-Temperature Superconductor, Al-Doped Sm-123: An Electron Density Study
✍ Scribed by Marco Scavini; Riccardo Bianchi
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 429 KB
- Volume
- 161
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Two Sm-123 single crystals of composition Sm 1.06 Ba 1.94 Cu 2.65 Al 0.35 O 6؉ (04 41) were annealed under reducing (T ؍ 7503C, P(O 2 ) ؍ 10 ؊ 4 atm) and oxidizing (T ؍ 4003C, P(O 2 ) ؍ 10 ؊ 1 atm) conditions. Their investigations by X-ray di4raction at room temperature evidence that both reduced and oxidized samples belong to the same space group, P4/mmm. Aluminum substitutes copper only at the (0, 0, 0) crystallographic position and it displaces to the (:0.06, :0.06, 0) site. Two oxygen ions in the basal plane are bonded to each Al ion. Both (0, 1 2 , 0) and ( 1 2 , 0, 0) sites are occupied by oxygen ions so that Al ions are in a tetrahedral coordination. The local structural distortion, induced by aluminum substitution, inhibits the tetragonalPorthorhombic phase transition.