Preparation and properties of (Y,Eu)-123 superconducting single crystals

Abstract

A series of single crystals with starting composition Y 1− x Eu x Ba 2Cu 3O 7− δ ( x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0) were prepared in Al 2O 3 crucibles in the self-flux method. A home-made setup for crystal growth and a new flux separation method are introduced. Eu-doped Y-123 single crystals were characterized by means of X-ray diffraction, energy dispersive X-ray spectrometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and AC susceptibility. All single crystal samples maintain the crystallographical structure of the 123-phase. The SEM and AFM measurements indicate a growth anisotropy. The growth of the (0 0 1) surface is related to different growth mechanisms, and the spiral growth mechanism is the predominant one. For the first time, we observed a regular array of groove on (0 0 1) surface. A drastic suppression of the superconducting transition temperature with Eu concentration was observed. Al contamination from crucible corrosion and Eu substitution for the Ba site result in a heavy reduction of T c in single crystals.