Mossbauer studies on novel high-T-c (Sn,Sr)-doped La2-2xSr2xCu1-xSnxO4 superconductors

For La2-2xSr2xCu1-xSnxO4 (x = 0.075, 0.090 and 0.110) superconductors, the effects of Sn-doping on local microstructure is studied by means of Mossbau er spectroscopy. The results show that Sn ions in the 4+ valence state domi nantly occupy Cu sites rather than La(Sr) site. In the view of the effectiv e oxygen content (or excess oxygen), the dual role of Sn dopant on the carr ier concentration is discussed. We attempt to explain the high transition t emperature T-c in (Sr, Sn)-doped La2-2xSr2xCu1-xSnxO4 samples under the mod el of amphoteric effect of Sn-doping on the concentration. (C) 1999 Elsevie r Science B.V. All rights reserved.