Structural and superconducting properties of the La1.8−xSmxSr0.2CuO4 system (0 ⩽ x ⩽ 1)

✍ Scribed by E.Ben Salem; B. Chevalier; P. Gravereau; F. Weill; A. Tressauc; J. Etourneau

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 538 KB
• Volume: 242
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)02422-7

✦ Synopsis

The phase diagram of the Lal.s_xSmxSro.2CuO 4 system has been investigated by solid state reaction at 1150°C in an oxygen flow. In these conditions, two phases have been found: (i) T-phase which exhibits a homogeneity range for 0~<x~<0.45; (ii) T*phase which is obtained as single phase only for x = 0.8. The thermal dependence of the unit cell parameters allows to correlate the occurrence of an orthorhombic--,tetragonal structural transition to the absence of superconductivity above 4.2 K for the compounds with x = 0.45 and 0.8. The tilting of the [ CuO6 ] octahedra (T-phase) or [ CuO5 ] square-based pyramids (T*-phase) provoked by these structural changes plays an important role on the electrical properties of the compounds. Moreover, the overoxygenation of the T*-phase LaSmo.sSro.2CuO4 induced by chlorination treatment, leads to the disappearance of the structural transition and the occurrence of a superconducting behaviour below 35 K.